Just wante to say that Installing Service Packs or patches doesn't degrade the speed or power of the computer but patches either improve perfomance and give better security, the fact that you machine gets infected every 1 or 2 days shows the IMPORTANCE of patches and service packs.

I mean it makes no sence keeping your door's locked and windows open.... you are still insecured..
anyway its up to you to update or even upgrade but after reading the document at sophos and microsoft only way you can stop this virus is installing that patch. belive me no matter how messed up your computer is patches will always help you and one more thing you can "ALWAYS UNINSTALL" a patch when you need too.