hi! i have a problem with my hard drive i THINK ok here is a rundown

i installed a game (mechwarrior 4) and i run it and it says a file is missing but its there.

i installed unreal tournament and installed infiltraion mod after that and it says that a file is missing but its there!!

and now with my free internet banner, its saying that files are missing tampered files blah blah blah

what wrong?:? has this happened to ppl b4 how can i fix it??? please any help i would LOVE!!!!!!!!!!!!!!!!!! thanx ppl for helping hope to hear from you ASAP!!!! BYA!