Problem with SATA disks!?

OK I have a computer running Windows XP system for quite a while now and use it rarely these days. It has three SATA HDDs and it always worked fine until today... I had a plan: i have three computers. Computer A has the two big capacity HDDs, B has one medium HDD, C has small HDD. I wanted to use one of the HDD in A and put on B and put the HDD on B on C. Basically I am aiming at copy all the files in one of the HDDs in A to another, then I can use the big HDD that has no used space onto comp B, thus replacing B with a bigger HDD. And move the HDD in B to C so all comp get a bigger HDD apart from A.

And the ultimate problem is, when I tried to figure out which HDD in A had free space by attaching it to B, i found out i unplugged the wrong one. I went back to A to double check which HDD physically should I plug into B and suprisingly found out bith large HDDs cannot be found, only the system HDD can be found. I tried all possible combinations to restore all cables, slots and HDDs in the exact position as it was working before but I get either no bootable HDD or two big HDDs not dispalying on my computer.

So I have no idea what happened, I just unplugged one of the HDDs and plugged it in again and found out none of the drives were found apart from system disk. I have important files on these two HDDs and I need to get this solved ASAP. I apologise for a long explanation but I need to get this fixed very soon!!!! PLZZZZ