Hello Bolox and FerchogtX, welcome to the Seven Forums.
Yes, as FerchogtX already told above, XP Mode is always 32-bit, even if you run it on a 64-bit system. You can not have a 64-bit virtual machine on Virtual PC, so even if you install XP, Vista or Seven from your own install media to a virtual machine, it has to be 32-bit.
XP Mode emulates hardware, it does not use for instance the graphics card of your host system. The GPU it emulates is an old S3 Trio 32
, which is not capable to run the most modern games. You can try; some older games run nicely on XP Mode.
You can not change the emulated GPU, so there's no way you install better drivers