How to remove spyguardpro

Dear friends hello from Athens - Greece. I am using Avast v4.7 Home, and have a problem to remove a downloaded maleware named spyguardpro. I didnt download any software, but one day I found 2 icons at my task bar (near the clock) and on mouse over I get this msg : "Windows had detected spyware infection. Klick here to protect your computer by spyware!". Any 15 seconds I get also a "Windows msg" like this : "Warning! Potential Spyware Operation. Your computer is making unauthorized copies of your system and Internet files. Run full scan to prevent any unauthorized access to your files. Clik here to download the spyware remover". From the icons near the task bar clock I get also a msg like this : "Windows antivirus. Windows had detected spyware infection. It is racommended to use special tools to prevent data loss. Windows can now download and install the most up to date software for you. Click here to protect your computer from spyware".
If I klick on msg, it opens a web site.

Please, help me !