Hello!
Today I'm inheriting my dad's laptop as he's upgrading to a mac, and after a year of my old laptop's graphic chip melting down I can finally play The Sims 3 again!
I'm good with computers, or at least in understanding them, but one thing I've been wondering is is it best to reset my dad's laptop to install my sims stuff from a clean slate, or simply leave it as it is and uninstall the programs I don't want, then install all the sims stuff?
The latter option would be easier as re-installing all the windows updates and such will take a while, but would the clean slate help The Sims 3 run better? (with all expansion packs up to Island Paradise except Supernatural)

Depends on how much crap there is on it. If it's gotten bogged down with a bunch of extra crap in the registry, has a lot of stuff that you just don't need, then wiping and restarting might help the computer run better in general. It won't do anything specifically for TS3, but if the computer's generally running better, TS3 will run better too. If its current performance is fine, then it's not going to make much difference.

Hm I don't think it's too bad so I'll leave it, thanks for the clarification
I don't know if you'll know the answer to this but I've seen various "registry cleaning" programs advertised over the Internet for a price. The best-looking being RegistryCleaner Pro. Do they actually work, or are the errors in your registry they scan and tell you about fake?
I'll go and install the game plus 7 EPs and 3 SPs now... Oh god. Somehow I don't think I'll be emerging from my computer seat for a long time now xD

CCleaner is my registry cleaner of choice.

Cleaning registry is a double edged sword and you should be very careful with it. If you're not careful the program can go overboard and delete things it shouldn't have, but if used by properly it can give provide a significant performance increase in bogged down systems.

For the most part ccleaner won't provide "fakes". It may however provide false positives. It will always ask you to confirm if you want yo delete first though, and it will make backups.