My computer was really sluggish. I thought it was time for the good old wipe. I loaded up my XP CD and each time it went into Windows Setup it gave me a BOSD 0×0000007B. My HD works. So I booted into Knoppix (CD) and wiped my HD clean. Tried to go into XP, but it said it didn’t find any hard drives connected to my PC. What is happening? I know my Hard drive works! how do i solve this? How do i reinstall XP without these problems?

Maybe the hard drive hasn’t failed completely yet, but it’s going to? Test the hard drive, you can use Hitachi’s drive fitness test. If you get errors during the test, most likely you’ll have to replace the hard drive. Also, make sure it’s properly connected to the motherboard. Reconnect the hard drive and try installing XP again. It might help.
Just in case, try low level hard drive formatting. For this purpose you can use Active@ Kill Disk Hard Drive Eraser.
It’s also possible that you have a problem with the hard drive controller on the motherboard but the only way to find out is installing a good known hard drive and installing XP. If XP cannot see a known good hard drive, most likely it’s a motherboard related problem.