If you just have to throw away money, Kaspersky Anti-Virus (which can be had from COSTCO for $15.00). There is really no point in spending the money however with Microsoft Security Essentials being free and oh so effective.....
want to test your anti virus?
copy: "X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*" (do NOT include the quote marks) into a .txt file or a word document....whatever.....see does your chosen anti virus identify the file you've just created as being harmful when you attempt to save the file. If it detects the file, your stuff works (at least as far as malware goes....). If it does not, you're in trouble.
The string of characters I have provided is harmless so don't be frightened by the test. DO IT, however. Read about the string of characters here:
http://www.eicar.org/86-0-Intended-use.html