I have a 20G HD right now and its full so I got a new 120G coming in the mail. I was doing some reading about how to tranfer games and apperently some games don't allow you to transfer the save files such as Forza 3. I can't find anything about Skyrim or Oblivion on google or here. Has anybody had any trouble with this?

The new HDD may come with a cable and transfer software. Thats how I remember doing it when I got the 120GB ~3 years ago. If not, you can just plug in a USB flash drive and copy all the saves over to that and then send them to the new HDD.

think you can buy such a cable otherwise

Yea I'm getting the cable. But I think I read it on the wikipedia page about xbox acessories that some games save files didn't tranfer. Even if they don't I can still just put them on USB and do it that way? I can use any USB right just format it?

en.wikipedia. org/wiki/Xbox _360_ accessories

Here it is. About half way down theres a list of games that have un movable content. Under the storage section.