memory problem with CS2

i've been using photoshop cs2 with 3gb of ram, and i was getting about 2.3gb of "maximum used by photoshop". as sometimes in bigger works i got the message of insufficient memory to run photoshop, and the same on lightroom, i decided to upgrade to 8gb of ram and to xp 64bit. something is very wrong here, i can't understand how, but i'm getting the "maximum used by photoshop" memory only 2786mb. so, i wasted a lot of money buying xp64 and more 5gb of ram, to get only more 300mb to work on photoshop? this looks like a huge bug in the program. is there any fix to this error?

It's not a bug.

< http://photoshopnews.com/2005/04/04/photoshop-cs2-how-much-r am-fact/>

here: < http://kb.adobe.com/selfservice/viewContent.do?externalId=32 0005&sliceId=2>

is refered that "The RAM above the 100% used by Photoshop, which is from approximately 3 GB to 3.7 GB, can be used directly by Photoshop plug-ins (some plug-ins need large chunks of contiguous RAM), filters, actions, etc. If you have more than 4 GB (to 6 GB (Windows) or 8 GB (Mac OS))"

but in fact, at the Performance Monitor even with huge images and working with a lot of layers, the used memmory never goes up of 4gb, but the xp64 shows that the 8gb are recognized. this seems weird :\