@Mouser: but doesn't 32-bit Win7 only recognize 4GB max?
EDIT: yes, 4GB is the max. Google is my friend! Win7-64bit can use 8GB.
4GB is max for client/desktop Windows versions, server editions can handle a lot more (8GB for Home Basic and below, 16GB for Home Premium, 192GB for the rest of the non-server versions).
E6550 CPU has dual-channel memory controller, so go by pairs
of memory (N-channel means striping memory requests over N ram blocks, increasing throughput). Keep in mind that memory speed is lowest common denominator of all sticks. Also, go for N blocks of ram (two in your dual-channel case), stuff doesn't go faster above the channel count - so in general, get as big blocks as you can afford, and leave the unused slots for possible future expansion.
That said, it's not a *problem* adding faster ram, it'll just run at the slower speed - worth keeping in mind since slower memory can often be more expensive because it's older. And as others have mentioned, you won't be upgrading this system much more, so go for two additional 1GB sticks.
I personally enjoy 8GB in my workstation, it has enabled me to turn off pagefile (with no problems for any app) and
use a decent-size ramdisk at the same time - YMMV. Never ever going to pagefile can be a big speed improvement; SSDs are fast, but RAM is still a lot
faster. If I was to upgrade to a new system, that would probably mean triple-channel memory and DDR3 rather than DDR2... I'd be in serious doubt whether to go for 3x2GB or 3x4GB sticks.
+1 for TrueCrypt, it rocks - unless there's some corporate demands, I can't see why you'd use BitLocker instead.
You might find that 32bit is better because you have hardware that has no 64bit drivers, eg. scanner, printer, etc that you can't afford to replace at the moment. Later when you've updated/replaced them, then you can reinstall with Win7 x64.
Was an issue in the past, especially with 64bit XP, and a bit with Vista... not so much with Win7. If you can't find a working win7-64 driver, there's a good chance you won't find a 32bit driver that'll work either.
Get a SSD now
- yes, they're ridiculously expensive, but they're well worth it. Use it just for your system files (OS install + apps) and if you have some data that benefits a lot from fast random I/O access (I keep my sourcecode on my SSD). Which size you'll be able to live with depends on your uses, but most people will
need an additional disk for "bulk storage". You need to closely
study SSD performance, as some of the drives out there work WORSE
in practice than mechanical drives. The intel SSDs are overall pretty darn decent, but there's faster (at least for some workloads) drives around that are cheaper. Haven't followed the market so I don't know what the current trends are, but I really enjoy my 64GB X25-E, and it's plenty big for the stuff a SSD is useful for. Some of the smaller SSDs also seem to be slower, so caveat emptor! - you should probably look around the 64GB or 80GB range to keep it affordable and still get great performance.
While most computer components don't carry over well to a new system, you definitely will
be able to carry over a SSD you buy now even if you build a completely new machine... and while newer & faster & cheaper SSDs might be around then, one you buy now will still
effortlessly beat mechanical disks, and be comfortable. The first SSDs sucked, the ones around now aren't that bad investments