Help with failing laptop (possibly hard drive related)

So, I posted this same message over at Tom's Hardware, but I like you guys too, and I'm all for multiple opinons, so read on if you want to help me out...and I know you'll want to ;P  Also, I don't really know where this should go, so I'm sticking it in HDD's and SSD's, if a moderator wants to move it, please do so.

 

Hey guys, I have an HP Pavillion DV7 and today it wouldn't boot. I would hit the power button, and the lights above the keyboard would light, as well as the power button, but the disc activity light on the front was not lit. The screen also remained blank, not even lit. I took the computer all of the way down and cleaned everything and re assembled it, same thing. Out of desperation, I took an old laptop that has since stopped working and installed it's hard drive to test if that was the problem (I don't really know the dangers of this, if any, I was just looking for an answer). When I hit the power button, the screen lit and it looked as if it was going to boot (even going to the windows xp loading screen), but then it would fail to boot and take me to a screen with a message, failed to boot and jazz (can't remember exactly), and gave me the options of starting in 3 variations of safe mode, with last working configuration, and normally. I tried all, and all ended the same way (probably because it was a drive from another laptop with other settings and even a different OS [the laptop that wouldn't boot is on windows 7, the canibalized hard drive had xp installed])...

So, I then re installed the original drive, and to my surprise, it booted, and I'm typing this message on it right now. My question is: what may have happened? Is my drive failing? Is there a way to check? Should I be worried? And finally, what can I do to fix this?

my Lenovo i7 gaming laptop does this all the time. Sounds like your hdd was loose. If you are truly concerned you could buy a new hdd, unless your terrified of faster disk performance.

Yeah, after doing minimal reading via my ipod when it wouldn't boot, the first thing I read was to check the hard drive, I unplugged it and plugged it back in twice (once to see if that was the problem, and the second time when I re assembled the laptop after cleaning it).  It didn't work until I had plugged in the old hard drive, and then worked again on it's factory hard drive.  I don't know what's up.