I would not want to run Vista on X505, especially with only 512MB of RAM. Check out the posts in X505 section, I believe Erik did an upgrade to Vista, it ran OK. Most XP drivers should work just fine.
which card did your X505 come with? PCWA-C300S(EU version) or C800S (US, JP)? You can check out the Sony support site for drivers. If you cant find it, let me know and I will get one from my install CD.