I took the my 20 gb hard drive out of my gateway and put it an my compaq en sff and won't boot operating system no errors pop up all cables are connected fine..

I'm sending you a boot disk that will get you going.I am dead tired right now or I could tell you how to do it. You need to transfer the system files to the new motherboard. It is either boot with a 95/98 disk and fdisk/mbr or sys C:. Someone else I hope will give you more insite.

or is it the slave master config?

Jason, That's like taking the engine out of a truck & putting it into a sportscar- the engine doesn't change at all but the connections, the timing, etc. are all different. Even if the car starts, it won't run right. You don't say what exactly happens when you try to boot but you might start by running "Repair" if you can get that far. Go to microsoft.com and look up Article - Q249694 for mor help...

The slave is fine it runs the pre startup screen not sure exactly what it's called but when it goes to run windows i get a black screeen i will look for somemore advise from microsoft .com thanx