I'm with f0dder in his response as the most pragmatic and current view. I'm a happy user of 64 bit OSs for several years now, and I think your biggest concern should be about the upgrade process rather than hardware/software compatibility as most of thoste issues are ironed out now. You might want to start with:
http://windows.micro...ntly-asked-questionsThat tells you that moving from 32 bit to 64 bit is definitely not something you can do easily as an "upgrade", so that may make it unappealing from the start for you. What that means is you need to reinstall all your apps and backup your data then restore it once you've installed the new OS. I certainly wouldn't liken it to a move to Mac, but it does require a full redo of your software environment.
The vast majority of 32 bit apps are 64 bit compatible. Of course you should check software compatibility lists for anything you might use and see if there are any known problems. Here are some resources:
http://www.microsoft...7/en-us/default.aspxMost of what you'll see on the non-compatible side are either very old apps, or apps that try to do something tricky with the deep internals of Windows (system hooks, etc.) that need to be 64 bit to hook into Windows properly, e.g. antivirus. Any currently updated app should have 64 bit support, and certainly if an app has Win7 support, it should.
Modern 64 bit apps are seldom noticeably slower than 32 bit versions, and in some cases faster, although due to the increased instruction size and memory use, there is certainly a theoretical performance penalty. In the real world it's rarely detectable these days. That being said, for any performance-critical app, you will likely need a well-tuned 64 bit version for performance equivalence or improvement, since these apps already tested the limits of the system at 32 bit. This is why earlier 64 vs 32 bit tests sometimes showed inconsistent results on benchmarks, with 64 bit pulling ahead in some cases, and 32 bit in others. As time has gone on and 64 bit becomes more pervasive, more and more apps are optimized for it. The advantages also become much more clear with large memory use scenarious, of course. This is an example of an older benchmark test where you can already see 64 bit pulling ahead in many cases, but some of the performance critical apps (like rendering) do show some inconsistency, and this is probably down to how well tuned each app was for 64 bit at the time (note the article was written 2 years ago):
http://www.extremete...,2845,2280808,00.aspThings have continued to improve since then.
Your SIW report is a bit confusing as it doesn't seem consistent in the memory limits it reports, but it does seem to say that - if you do have 4GB - you're already missing out on some of that (it's only showing about 3GB). I would imagine your board can support at least 8 and possibly 16GB of memory, which is somewhat supported by parts of the SIW info (but again that is inconsistent). It does appear that you have 4x1GB DIMMs so one disadvantage to upgrading is you'd have to get rid of some of your existing memory, trading out for e.g. 2GB DIMMs. Even upgrading to 64 bit without a memory upgrade would give you access to a bit more memory though it seems.
In any case as I said at the start the biggest issue is probably the hassle of reinstalling everything. If you're ok with that, and given you're a Photoshop CS user and could theoretically benefit from 64 bit, then I think it may be worth the upgrade. But take your time about it, make sure you back everything up, and be prepared for the full reinstall process.
- Oshyan
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I wasn't sure what he was going to do with it at first since it doesn't fit, so what came next was a bit of a shock, but oddly satisfying. 
