2000 Pro Installtion?

For the last couple of weeks l heard a cry come from my IBM thinkpad 600x, "USA", l laughed. This went on for a while until last week when l turned on my computer it was opening at the speed of a snail, maybe slower.today when l turned the computer on it was starting real slow until the screen said it was checking my password and then stopped cold. Now it doesn't do anything but say IBM Thinkpad.I bought my laptop on ebay from an IBM reseller who preinstalled the windows 2000 and on the bottom of my computer is a COA from microsoft. If l had the disk l would try and reinstall the program but l do not.I forgot the name of the reseller and they we fantastic to do business with. They helped whenever l had a question and always told me if there was ever aproblem l should just send it back and they would correct it. In fact they are in Atlanta and l had my computer there and l had a problem with the dvd player and when l told them where l was they said come right over and they will get it going. p.s. my son fixed it and l never went over.