BWAAAAAAAAAAAAAAHAHAHA! Whoa, buddy, have you forgotten how slow a K6 is? Win2000 or XP almost certainly won't run with all his old hardware, presumably low memory, and small hard drive.
I have an old K5 running a dualboot Dos6.2/Win98 with 24M ram (mostly as a printer buffer). The Win98 partition needs to be cleaned out regularly.
So, delete all your temp files and subdirectories (under c:\windows\temp), all your internet history files and subdirectories (under c:\windows\history), check for any other overly full direcorties or old backups that you may not need anymore (particularly old games), and then run Oldeconomybuyer's directions in post#6.
Also, if you have it handy, Norton's DiskDoctor and Speedisk are much better than than Windows Scandisk and the ultraslow Defrag.