thinkpad 600 or 600e? I do not think that you can load XP on either model, unsupported hardware. Anyway someone else may have a workaround that will allow you to load XP on that unit but I think that a better option is to upgrade to a newer platform. I work with a lot of IBM laptops and your hard drive making it this far is amazing.
Another thing to look at is the display, it should be somewhat pink at this point in its life, that is the cold cathode lamp that is used for the backlight on the display. Once the display goes pinkish it will not be long before it goes out completely.
Yes I know this is not what you want to hear but it is just the facts and I also know that new laptops are not exactly cheap, but in the long run your best bet is to upgrade.