What are you protecting from? Spyware is intrusive, annoying, but not very dangerous, compared to the *unknown* programs that can get in via the same routes. (After all, you are asking about antispyware, so I am guessing there are some holes left... ;-) )
I'd recommend fixing your system, instead. Anti-spyware programs are a crutch. The concept of 'cleaning' is nonsense - wipe and rebuild (or restore from known-good backups). And if you actually need anti-spyware, you have enough holes for something nastier to slip through.
Note - anti-spyware and -virus is good if want to lessen the chance of broadcasting your documents and/or pr0n habit to the world, or being turned into a spam relay or DDoS bot. Thus, they are tools to make computer administration easier. They don't work if you want actual security (like, being reasonably certain that none of the above will happen EVER, instead of 'not too often').
P.S. Fixing your system is much helped by using anything other than Windows - I'm partial to OpenBSD, but any Linux distro will do much better; using anything other than Internet Explorer - for example, Firefox or Opera; and using anything other than Outlook (Express) - for example, Eudora or Thunderbird. You've already got a NAT router, I suppose, so that's good. You might want to upgrade to a firewall (i.e. something that filters outgoing traffic too, at least).