For small to medium sized scratches, I know there are a lot of products out there that can get rid of them. We bought ours at Best Buy (has a wheel shaped mechanism that you place the CD in after a few squirts of some "magic" liquid - and then it "buffs" out the scratches). It does seem to work about 90% of the time.
As far as the game freezing though, I am sure others will be along that are more "technical" than I am, but the first thing I would try would be the drivers (just making sure they are all up to date) even a new computer may not have all the drivers updated.