In regards to your task manager screenshot, check out the process "dlhost.exe", after some googling I came across this:
Windows errors related to dlhost.exe ?
dlhost.exe is an advertising Spyware called IamBigBrother. This process monitors your browsing habits and distributes the data back to the author's servers for analysis. This also prompts advertising popups. This process is a security risk and should be removed from your system.
Note: dlhost.exe is a process which is registered as a trojan. This Trojan allows attackers to access your computer from remote locations, stealing passwords, Internet banking and personal data. This process is a security risk and should be removed from your system.
This possibly could be hogging some cpu usage but isn't exactly showing it via task manager. My suggestions would be to save any important data ie. docs, pics and do a clean install. Who knows what else he has on his rig. Go to c:/windows/system32 and view by details, sort by date and see if anything newer has been created, most likely you'll see a couple .exes with wacky names, those are either trojans, malware/spyware.