cannot remove winPCdoctor. is it a virus?

Ever since I got the Avast antivirus, I tried to remove al those stuff like malwarewar virus heat using the add or remove programs, but i can't seem to remove this WinPCDoctor.and windows and xp antivirus also keeps irritating me with popups

 

see, another one by XP antivirus is here:

 

WARNING! 44 infections found!

 

Unwanted software (malware) or tracking cookies have been found during last scan. it is highly recommended to remove it from Your computer.

then they give crosses and show the following:

Lost Documents and Settings

Permanent Data Loss

System not starting up

System slowdown and crashes

Loss of internet connection

Infecting other computers on yor network

 

then they give me two choices:

remove all threats now

continue unprotected

 

I know I will have to pay if I select the first choice, so I choose the second

but it keeps popping up