On this Fujitsu T900 Core i5 (1st gen), it had windows 7 installed on an ssd. Then I took it out, put in another one to try windows 8. Much to my dismay, the touch drivers for windows 8 did not work. So I put the SSD with windows 7 back in. However, I get a blue screen everytime I boot, and startup repair doesn't seem to be doing anything. What should I do?
I do not have the complete answer, but the problem is most likely that the Windows 8 installation put your BIOS into "UEFI mode". It has to be put back into "legacy mode" for Windows 7 to be able to run.
Your next step is therefore to figure out how to get your BIOS back into legacy mode, and I do not have an answer to how to do that. But maybe this information can get you a bit further.