Ok, first of all Fabre, you I would like to recommend you to a thread I made on the lq board not long ago, which helps with installing ATI, on 10.2, but I suspect it won't be much different for 10.1, seeing as the two OS' are so similar.
The first thing I would recommend doing is, upgrading your current version of which, if you haven't upgraded it yet, it should be X.org 6.7.0-3
to the latest version currently available, using Mandrake Linux Update.
after you've done that, have a look at this thread:
It was a huge help me to, and I would like to take this time to thank all the people who made it all possible, in the original thread, currently hosted on www.driverheaven.net
; without them, I would have been lost forever.