HELP iTunes wont download!!!

I used to have iTunes on my comp for ages but about a month ago we got a virus and we lost everything, we've got it fixed but I cannot download iTunes now the following message comes up after the thing has been downloaded, it's in a box and reads
D:\Documents and Settings\David\local settings\temporary internet files\content.IES(or 5)\29S(or 5)JPQJJM\iTunesSetup(2).exe

then theres a Red X with the same as above with "is not valid Win32 application"

Can someone tell me what to do? make it a easy step by step thing as I aint very technical!!

Thanks in advance!