Right, Was deleting some files on advice from another forum about removing spyware and i deleted the wrong one

now it just starts up and runs windows but wont do much else, i also cant access the start menu. Is there a way to do a system restore? i've tried starting in safe mode and clicking system restore from there but it wont do owt

BTW this aint my PC so if i dont reply soon you know why.
Cheers in advance