One of the latest spyware/trojans. POPS up on your computer , "keep your 2009 Microsoft antivirus up to date. Get a free scan and protect your computer". If this does pop up... DO NOT HIT CANCEL. Attempt to close the window normally Or just shut your computer off. Then after turning it back on... If you get any pop ups similar to the original...You are already infected by a trojan that takes control by slowing your computer down and asks for $$ to get it going again properly. This is something out of the wonderful "Eastern Block". You can try superantispyware.com to get this out of your PC. Use the Free edition. It has worked for many.
My Yahoo spam catcher , caught it and it looked fishy to me so I deleted it . I've had no problems !
When a suspicious screen pops up ALWAYS use the 'X' button to close the window or if you can cles the process in Windows Task Manager ( do the 'Ctrl-Alt-Delete' button combo to get it up on the screen).