Romulus68 said:
Friend needs to stop an Ex who is accessing her computer, getting in her emails, etc.
To
test whether an antivirus is working or not, use the
Eicar test file rather than risk infecting a PC with actual malware. However if the malefactor is technically competent, the most secure course of action would be a Windows reinstall (to ensure the removal of any rootkits) followed by the installation of appropriate security software.
It may not just be the PC that needs securing - if webmail is involved (GMail, Yahoo, Hotmail, etc) then the account passwords should be changed also (and check the settings to see if the account has been configured to send copies to emails to a third party). If a wireless network is being used, that needs to be encrypted (using WPA preferably) to guard against eavesdropping.