Windows XP!!!! Price...

  Microsoft decrease a price? Not likely. You can buy an OEM XP Pro SP2 disc for considerably less than the cost of the Microsoft disc. Just make sure you purchase it from a reliable store.

When Microsoft interviews a candidate for a job they ask if they know what lowering a price means, if the candidate knows, they are not hired. You can get OEM XP in the US at newegg for $90, which is definitely the way to go unless you own a lot of Microsoft stock.   Catmoves is correct get it from a legitimate dealer, if you find a version at a really significant discount, it's very likely a pirate version, which will only cause problems in the long run