Before doing anything, why not investigate the possibility of trading the 32-bit install disc for a 64-bit one?
At 4GB you're right on the edge of where either kind of works, but I honestly figure 64-bit is the future and so you may as well familiarize yourself with the landscape. That and you'll get to actually use that extra 0.5GB of RAM with the 64-bit version over the 32-bit one.
I placed an order for this sytem;
Intel(R) CoreT i5-750 2.66 GHz 8M L2 Cache LGA1156
EVGA 9800 gt 512 mb
750gb HDD
4GB (2GBx2) DDR3/1600MHz RAM
EVGA P55 LE Intel P55 Chipset
700W PS
Now I have a choice;
Buy Windows 7 Ultimate 32-bit from my school for 15$, or buy Windows 7 Home Premium 64-bit for 105$
Would you say it's worth 90$ for 64 bit > 32 bit? I'll be using it for basic web browsing, MS Office, and the occasional game (Mainly just FPS, I'm sure I'll get Crysis soon). Oh, and I'm on a somewhat limited college budget.

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