Win 7 Asus MA479 8GB Ram hard drives are 500GB The operating system was a Caviar Green, and I tried to exchange it for a Caviar Blue. The Caviar Blue took the install correctly, but the Green, the prior operating system hard drive, will not allow itself to be used as an external hard drive. I use TrueCrypt and tried to format the Green and it freezes each time at the very end of the encyrption of the partition. I took the Blue out of the system and tried to encrypt it, and same problem. I think there must be something on the hard drive that shows it was a system drive and it causes a conflict. I have tried writing over the system hard drive to fully erase everything but that does not work, it still freezes. The drives will work in a different pc, i.e. other pc where it never was the system drive. The external hard drive is connected esata through Thermaltake. I have used TrueCrypt on various pc's for years including this Win7 with no problem. Thank you.