Windows Installer Problems?

So… I've been trying to update my iTunes from 6 to 7…I've updated every version from 4 to 6 of iTunes…but when it comes to 7, it just won't install…I keep getting a message that says: "This installation package could not be opened. Verify that the package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer package." Been at it for a week now…and still can't figure out how to fix that… Can someone help plz? Thx

sift thru this and see if it helps any:

http://discussions.apple.com/forum.jspa?forumID=792

shelf life

Thanks for the site!! I checked it out and tried to see if any of there problems was like mine…but, to no success… I think I figured out its more than iTunes…cause I tried to install winzip…of all things and I get the same message as stated above… So I believe its a problem with Windows Installer…I tried to check out the windows site and downloaded whatever is the current version of the install…and still I end up with the same problem… So I guess I still need help…lol!!