bad instal media/corrupt file mess

I've been having this problem for 2 days now trying to re-install Return to Castle Wolfenstein:Enemy Territory...

At 86% install, it stops and I get a message 'An I/O error occurred while installing a file. This is normally caused by bad installation media or a corrupt installation file'...then a little window pops up after I remove install with 'Corrupt installation file!'.

It's also done this twice at 1%, as I've DL'd the file(wolfet.exe) 10 times from diff sites since reformatting my comp last night.

Could every file be corrupt?

Try cleaning your CD very well, it could be something as simple as a smudge on your CD that is not allowing the installation to complete.

I'm not using a CD, it's a free mp DL.

I haven't had this problem before, and don't know wtf the problem is. I'm told it might be my ram, but I want to exhaust all possibilities before bringing comp to get serviced.