You did not mention how much ram you have got. The newer the distribution the more ram you need. KDE 3.5 based like Kanotix Excalibur you could try on it with at least 256 mb ram. Usually i would suggest to have at least 512 mb ram. Win + A/V tool requires about 1 gb ram to run smoothly. Btw. you don't need to buy a licence, the key should be printed on a sticker, so you only need a xp home cd, which should be easyly to get. As sidenote: on a 1 gb ram system you could install Win7, with 32 bit usually old xp drivers also work.