Download one of these Bootable AV CDs....
http://download.bitdefender.com/rescue_cd/ (this one also updates itself over a DSL line at bootup)
http://dnl-eu10.kaspersky-labs.com/devbuilds/RescueDisk/
http://dl.antivir.de/down/vdf/rescuecd/rescuecd.exe
then burn the ISOs to CDR and boot his computer up with them.
Then scan (try to update the BD one, if using that one).
Afterwards install Comodo Firewall Pro, I guess AVAST if you want a free AV and SpyBot as well as FF with Noscript.
AV products are more or less what you pay for - they're all basically good - the non-free ones, at least. I'd avoid Norton as it is buggy and bloated though but
ESET, BitDefender, Kaspersky, McAfee, F-PROT, TrendMicro etc - are all good.
Tell friend to enable his file extensions in Explorer
Not to download any EXEs, including keygens, cracks, screensavers and other junk from non-reputable sites, find serialz and use those instead (ie just read the no's off)
Install SpyBot and Comodo FireWall pro and OK all the apps (the ones scanned already)
Use the SpyBot Immunise function (also after installing FF)
Install an AV
Install FF with NoScript and AdBlock Plus
or just buy a Mac and he won't have problems/issues with this rubbish.