.dll files

I was removing useless programmes off my pc with macafee virus scan. Well I happen to accept some default lists. After that I could not reboot my pc, the 1st error I encountered was no Himem.sys file, I copied that file from another windows 98 machine and installed it. Now I have this error that the .dll files has been affected. How am I supposed to fix this and what are the .dll files.
thanks
JD