I am running Xp, and I must say it is by far the best Microshaft OS I have used yet. I tried Linux, but I do alot of audio editing and recording on my computers and alot of my audio programs freaked out when they saw Linux. Unfortunitly I was raised on PC and have tried to switch to Mac, but its like trying to learn to bat left handed. If the audio software companies would make more programs Linux compatible I would use my D: drive alot more. I tried Win2k Pro on my 1.6 and it crashed in less than a week. I have noticed more speed after my computer has been off for awhile, but I have 5 fans and I leave at least 1 side off at all times, so it runs fairly cool all the time (except when I game, my gForce2 Ultra get hotter then the herpes from a taiwanese whore).
