There are many places for temp files to be - windows hase them, firefox has their own, they can be all over the place. It is virtually impossible to have all of them be infected, but cirtianly enough to be a nuisance. If AVG says 'hey look a virus' you really need to let AVG do its thing - weather it be heal, quarentine or delete them. If they are actually viruses it will do one of these three things if you let it. You should never not allow an antivirus to get rid of a virus unless you really like viruses and want them to spread to your other files.
If you are using XP there is a cleanup wizzard you can use to delete your temp files - some people will tell you that its bad to delete temp files, others good. They are both wrong. If you neevr delet eyour temporary files you will accumulate junk that you havnt used in 10 years on your hard drive which is space better used tfor movies, games, or other entertainment. If you constantly delete your temp files then your computer will have to redownload or re load those files fresh everytime you use your web browser or what ever else you do. Note that some see that as a good thing, and others see that as a bad thing.
No matter how you see it, a virus is a virus and you need to get rid of it before you worry about anything else. Doesnt matter if it infected explorer.exe - if its a virus, delete it before it spreads - worry about colateral dammage later or else it will be 3 times bigger.
If you find that you get virses you may want to think about using a better program than AVG.
Also, i think i heard a hospital say the same thing about people once - there are just too many to heal so they gave up. CMON man, what do you mean too mnay to heal?
