He was referring to upgrading to vista, just the 32 bit version if you wanted to, if for no other reason, then to get the dx10.
Personally, I wouldn't respond to that post, it seemed uninformed, confusing and just weird.
There is NO reason to not upgrade to vista 64bit, oem's are now pushing it by default so customers can use the 4gb's of ram.
There WERE, issues with 64bit software in the past, but I personally have found zero issues, I use everyday software including numerosu games and have zero issues.
If there is a usage of ram problem eh, you have 4gb's so I think your good. My windows uses up on average about 30 percent, that leaves 70 percent of 4gb's for applications.
It really isn't a problem, go for 64bit, it gives EVERYTHING 32bit does and adds the full support for 4gb's or more of ram.
Just do some simple research on vista 64bit via google. OEM's wouldn't be making it the default operating system on current systems if it wasn't ready for prime time or had issues with software as it once did.
Just do it.