There's an updated version of StrmExt available here: http://redwoodal.sweb.cz/StrmExt/StrmExt_mod_1.0.0.5.7z

This version fixes a couple of bugs and lets you edit the ADS, (using RWStream.vbs - you need to hit Cancel when you finish adding stuff).  See my post here if you want to right-click add an ADS called URL.

Here if you want the PowerShell version.

Sometimes when the sources dry up the only way I could find a download was to use the original download filename.  Like My Super Duper Utility version 5 might have a download name msdu5.zip.  Sometimes a google will pick up a copy sitting on a university server when nobody else is still hosting it.

Sounds like a meeting of AA

"My name is 4wd and I am a download whore."

Well I used to be but I never bothered keeping info on links/pages where I got downloads, just looking at the file name as was downloaded is usually enough to tell me what the file/program was for or did.  The few times my memory failed me it was always a simple matter to look at the properties of either the installer or installed program to give me enough info to find it again.

I look at tackling a search engine as an exercise in lateral thinking rather than a chore ... I always find something interesting even if it's not what I was originally after.

Let's just give you stuff. Filenames? Like 'StrmExt'?

They must like you, top result in Google, Yahoo, and StartPage was StrmExt.dll on x64 Windows for me, (not bad considering I'd never used Yahoo before).

Here's a Paste to ADS version in Powershell (needs v3+), requires no external programs and trims the URL to the last occurrence of '/':

#############################################################################
## Paste2ADS.ps1
##
## Uses: Get-Clipboard by Lee Holmes (http://www.leeholmes.com/guide)
##############################################################################

<#

.SYNOPSIS

Retrieve the text contents of the Windows Clipboard and write to file ADS

.EXAMPLE

PS >Paste2ADS.ps1 somefile.exe

#>

param (
  [string]$file = $(throw "Paste2ADS.ps1 <file>")
)


function Get-Clipboard
{
  Set-StrictMode -Version Latest

  PowerShell -NoProfile -STA -Command{
        Add-Type -Assembly PresentationCore
        [Windows.Clipboard]::GetText()
  }
}

$clip = (Get-Clipboard)

$count = [regex]::matches($clip,"/").count
if ($count -gt 2) {
  $text = $clip.SubString(0, $clip.LastIndexOf("/") + 1)
}

Set-Content -Path $file -Value $text -Stream 'URL'

It's assumed to live in C:\Scripts otherwise edit the Paste2ADSps_install.reg file to reflect wherever you've put it.

"         The few times my memory failed me it was always a simple matter to look at the properties of either the installer or installed program to give me enough info to find it again. "

BUT  You are a YOUNG "Whipper-Snapper" 4WD  Look at me  That is a Real Pic!  (well... Not the sword part  )

I've been reading this discussion on and off for a while, and it puzzled me. I just now read through most of it again, and I'm still puzzled. It seems unnecessarily complicated and too much like hard work.
The requirement seems to be:
When a file is downloaded, how to attach:

• (a) the source webpage URL - and/or the actual download URL - to the downloaded file (once it has been downloaded), together with
• (b) any relevant notes/metadata that may be of use as a brief reminder in future as to what the possibly obscurely-named file was about in the first place.

This is arguably a common problem that we might all face at one time or another, and I have certainly found it to be a recurring problem in my experience, and it can be addressed by realising that it doesn't really need any more data capture than can be automatically captured by default at download time, and it is apparently not necessary to attach the URL metadata to the actual file.
For example, I started off with a sort of "lazy man's minimalist approach" with the following steps:

• 1. Download tool: Always download files of any variety (and especially application installer files) using GetRight (invoked via the FlashGot extension in Firefox and as an Add-on in IE). 
• 2. Destination: Ensure that the default download is in all cases set to the same "bucket" - a working directory (C:\...\Download) and this is not in a User subdirectory. If GetRight finds it's downloading a file of the same name as one that already exists in the Download directory, it increments the filename.
• 3. Persistent log: Ensure that the GetRight settings are such that a single text file is used as an incremental log of each and every download - named C:\...\Download\Downloads.txt. At this point, any downloaded file can be identified by its filename and Modification date, which will correspond with the filename and download date in the log file. The log file will show the download URL for that file.
• 4. Attach further metadata: If I wanted to attach some further information to any given downloaded file at this point, I could do it in the filename or the Comment field (Alt-Z in xplorer² to replace, append or remove text in the Comment field).
• 5. Periodical housekeeping: as and when needed, move the files to appropriately structured libraries - e.g., document files to a document library (directory) and application installer files to an application archive directory and then into appropriate sub-folders representing application categories/types.
• 6. Filename preservation and renaming: In the process of doing step 5, adopt consistent file-naming conventions. Apply precise naming to document files and rename any generic-named application installer files - e.g., (say) "setup.exe" or "setup.zip" - to specific names, but keep the original name as a suffix - e.g., (say) "CleverApp v2.5.2 - setup.exe", or "CleverApp v2.5.2 - setup.zip". Thus application installer files can always be traced by the two relevant keys (name and date) in the download log text file. I have recently adopted this sort of filename preservation for scanned PDF document files sent to me in email, so that they can be traced back to the originating email they were attached to.
• 7. Replace downloads log: When C:\...\Download\Downloads.txt gets to about 2Mb, increment its name and create a new, empty file Downloads.txt. You could thus eventually accumulate incremental logs going back several years (if required), in the download directory.

Usually, I would not be too interested in subsequently tracking back any document files to the source, but application installer files were/are a different matter, so I am quite rigorous about the above steps.
My methods have changed somewhat since 2008 when I started to progressively learn how to use MS OneNote. I now maintain and update brief installation notes in MS OneNote for when I install applications/updates from downloaded application installer files, and - where space is not at a premium - those notes may even include a duplicate copy of the application installer files used, thus making for a self-contained set of notes and source files, in OneNote, on OneDrive, so that I could access those notes/files from any client PC. This gives ready access to acquired knowledge and a second backup contingency (I periodically back up all files to a separate primary backup device anyway).

Here's a screen clip of xplorer² showing some application installer files in my archives, displaying the extent of the metadata, most of which - and often already including data in the Comment field - is automatically captured at download time. The download URLs are stored in the readily accessible and backed up, separate C:\...\Download\Downloads.txt log file(s), with filename and date keys, if and when they are needed.

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