Pretty general question here guys as I'm away from my PC at the moment but I'm looking for any pointers to help me out:

I've been running Vista 32bit for a good while now, nice & stable @ 3.2GHz but a few days ago installed the 64bit version & my rig seems to be running slow as hell when it comes to running anything HDD intensive (defrag, file transfers, updates etc)

The only changes I've made besides the OS is to add another 2 sticks of RAM. Unfortunately due to no stock I've now got 2 different types of RAM:
2 x 1GB OCZ SLi PC2-8500 (original)
2 x 1GB Geil Black Dragon PC2-8500 (new)

I havent changed any BIOS settings & can run OOCT & ORTHOS stable for 24hrs in blend.

I'm wondering if the 2 different sets of RAM would cause any issues or am I missing some driver update since changing over to 64bit? I know I'm asking a very vague question here but I'd appreciate any kind of pointers.

Thanks in advance