Missing files?

My computer has 3 hard drives, a 20GB, a 40GB, and a 60GB. When I try to boot, it finds a boot record on the 20, then claims that himem.sys, dblbuff.sys, and ifshlp.sys are missing. Then it says it can’t find win.com. The computer has always bootedfrom this hard drive, and the only thing I have done differently lately is removing the 60 so I could ghost it on another computer. Why in the hell would it be doing this? I have important files on the boot drive, so I can’t just reformat it and putwindows back on it. My system specs are
PII 450
327MB of RAM
Windows 98