If you are using the recovery console your loss will be minimal (if it crashed in the middle of something that you did not save then you will lose the changes). If you are doing a "restore" from a restore point then you will lose anything that you changed after that date.
Guess the question was about a repair install, i.e. second repair option when booting from Windows cd. The point of a repair install is that you don't loose your data and settings. Would nevertheless backup the most important things to be on the safe side if anything goes wrong.Usually it doesn't. Also you may have to reinstall some drivers after a repair install.
Get some more information from http://www.webtree.ca/windowsxp/repair_xp.htm
Going back in time with a restorepoint only affects dynamic data e.g. a program or systemfiles installed after the date of the restorepoint. just reinstall (or not if that caudsed the problem).
"Dead"data like Word-documents will not be lost.