.mdf and .mds files?
 

I am wondering how i would use cracks with these file extensions .mdf and .mds i never used the before i used iso's but not with those extensions and i also used the fixed exe's.

Please help i need to know how to use these files.

Thanks
-Stashes

You didn't mention what game but since you mention 'crack' files I presume you got the mdf and mds files from GameCopyWorld as a crack?
If so, they are most likely a 'Mini Image' which needs to be mounted in a Virtual Drive.
When mounting the 'mds' file into a virtual drive it will appear as a proper CD/DVD image but it is actually only a very small section of the DVD, the mini image only contains the Copy Protection which tricks windows into thinking you have the real CD/DVD in the DVD drive allowing you to play the game without using the real discs. A game cannot be installed from a Mini Image but it will let you play an already installed game.
Hope that is understandable. ;)

GTA SA it used to work but now it doesnt it just minimizes im thinking it was just the crack i was using before but not sure

still doesnt work i mounted the .mds file do i need both mounted or just one?

Yes, you have to mount the .mds. (It will get the .mdf "also mounted".)