PC Security 2009 malware issue

Today, I got a call from one of my customers stating that they have some pop-up requesting that the they purchase software to remove virus' and spyware from their computer.This turned out to be PC Security 2009 malware.

I downloaded Malwarebytes Anti-malware software from malwarebytes.org to remove this threat.

I killed the PCSecurity2009.exe process via Task Manager.

Deleted the folder "c:\Program Files\PC_Security2009". Then ran a full scan of Malwarebytes s/w to remove reg edits and check the system.

She's okay now, but don't know how she is the only one getting re-infected with different pieces of spyware (just had a thought to check for rootkits).