At one point my pc started running really slowly with OS2.
After some initial frustrations, where it only seemed to be OS2, and not all my other programs, I found out that the major reason was overheating caused by *dust and fluff*.
Everything was back to normal after I blasted the inside of the pc with my air compressor.
That said, have you tried running Valley Benchmark from Unigine?
That is definitely going to tell you whether it is OS2 or the pc.
Not saying that the cause is dust and fluff. Merely that it is a contender until proven not to be.
