Ide for raid

Solution
You can RAID any 2 drives but RAID performance is always based upon the drive with the lowest capacity and slowest read/write specs.

It would be a waste of time and you would see no benefit with those 2 drives in RAID.
You can RAID any 2 drives but RAID performance is always based upon the drive with the lowest capacity and slowest read/write specs.

It would be a waste of time and you would see no benefit with those 2 drives in RAID.
 
Solution
you would need to find a RAID controller that will do both SATA and IDE. There are few that do this, but they do exist. Another option is to get an SATA to IDE adapter for one drive. However, like Dereck said, it would be a waste to RAID those 2 particular drives as you would be limited by the size and speed of the 40GB drive, and your 160GB drive is likely 2x as fast as the 40GB drive anyways. Also, some controllers are picky about mixing and matching drives, and will require you to use identical drive to begin with, so keep that in mind when planning out this project.