Deleting games installed via someone else's Steam account

[davidgn]

So, I'm asking for a friend of mine. A bit of a dicey situation.

1. She had a visitor install a bunch of Steam games on her computer, then take a hike (permanently).
2. She doesn't use Steam herself and has no account, and she's not able to remove these games properly without logging in. (Windows just launches Steam and asks for a login).
3. She also has installed separate versions of some of the same games her visitor installed (from from DVDs, Humble Bundle, etc.) and doesn't want to lose those installs or the game saves associated with them.
4. She's afraid of uninstalling Steam entirely because she fears losing all chance to get these things uninstalled properly
5. She would be more than happy to get rid of Steam itself as well after she's gotten rid of these other game installs that are clogging up her drive, while retaining her own parallel non-Steam installs of some of the same games.

So, what is the best way forward for my friend?

[Falro the Great]

Delete the Steam folder under C:\Program Files (x86)

[¸מטסﬣ]

Simples!

[Vault Hunter 101]

Tell her to uninstall Steam and then remove Steam folder (Default C:\Program Files (x86)\Steam)

Edit: The games will be uninstalled properly and won't cause any problems