Here, for my friend, a new computer is equivalent to 3 months (gross) salary, but the computer isn't the problem, the problem is HIM
The problem with the computer is you don't know what he's done so it's very hard to say what needs to be looked for and to be sure you've removed it all if you do find something nefarious. An IT PhD doesn't necessarily mean he know enough about Windows to be really sneaky but he might.
Short of shelving the existing system and buying a replacement, the safest thing to do is reformat and reinstall everything from scratch.
Don't use backups as they will likely be affected as well. Change all the passwords for all her on-line accounts (e-mail, Google, Facebook, etc and so forth) - do this from another computer in case it is a keylogger and it's still there. It's a pain I know but the options are limited.