I am helping a family member with a dead hard disk. It is a seagate 200Gb 3.5" HDD in one of those old-school external enclosures. The problem was that windows failed to detect the hard disk when plugged in through USB.

I removed the hard disk from its enclosure, and plugged it into my desktop PC. The BIOS does detect it upon POST, but unfortunately windows 7 would refuse to boot. It will get stuck on the loading screen with the glowing windows logo. Safe mode doesn't help either.

What options do I have before going for some professional data recovery?

edit: Someone modified the Title to something completely different from what I was asking, i just changed it back.

1) 2 HDD drives, DiskA(Dead), DiskB(my OS disk)

2) when B is connected to my system, everything works fine

3) when A AND B is connected, failure to boot. POSTs fine, but windows wont load

4) A has NO OS, its PURE data. It came from an EXTERNAL HDD enclosure which doesnt belong to me, and im trying to do data recovery.