Hard drive performance question?

Having a 1TB hard will not slow your computer down at all. Just remember to keep it defragmented. For a gaming HD, you probably want at least 7200 rpm. You can get up to 15,000 rpm on a WD VelociRaptor drive, but you'll pay more than 70 quid. The 32 MB or 8 MB in the names of the HD is the size of the cache. The bigger the cache, the better. The cache stores data that you just used, and it is faster than reading data from the disk.