Windows me lost files

I have windows ME installed on p/c and recently
got some virus, now when p/c gets loaded up I get error msg saying that I am missing mshtml.dll file and I cannot go anywhere else. I tried to overlay with windows me cd and get fatal
errors about 1/2 way thru, could I try to overlay windows XP or Windows 98 instead? I have alot of information on this p/c that I dont want to lose. Any ideas? Thanks