Help virus on my computer!?

As soon as my computer starts up the background changes to blue and in the right hand corner a box/window pops up and says my computer is infected and to run this MS Removal antivirus. I have never seen this on my computer before so Ive tried to run my regular anti-virus Kaspersky but every time I try and open it the same kinda box comes up and says Application cannot be exectued. The file avp.exe is infected. Please run your antivirus. I dont know what to do.