Hi!  Ok, I know it's old as heck but bear with me... specs... 400 watt PSU, Pentium 4ht 3.6 ghz, 4 gigs 5300 DDR2 ram 2 IDE HHDs. And just bought (thanks to EBay) a Radeon 3850 gpu.  

Ok. Upon install the CPU fan revved up to full blast, the computer beeped to post, seemed to "hang" then booted into a black screen that read "the pci e device is 2.0 and will run at 1.0 press F1 to enter setup..". I expected this to happen so that's not an issue, annoying that it says that all the time but I can live with it.  My main issue is the older games that I play on the 4700 are "lagging" now.  The specs of the hardware are way above what the recommended specs for the software are so running the games on high settings shouldn't be an issue, right?   Any suggestions? Reinstall driver? Purge GPU cache?  Anything else??   TIA