OK guys, I am officially at the end of my tether so if this seems like a rant I apologise but I really really need some help! I have a Late 08 MacBook Pro - 2.8Ghz. Which has been upgraded to 8GB of RAM. The hard drive it came with was a 7200 RPM 320GB. I need a larger hard drive. Files have got larger from my cameras and now some video too so I bought a 7200RPM 750GB WD Scorpio Black. Installed the drive put Lion on it and every 30 seconds it froze. Thinking the hard drive was a dud I arranged a replacement drive with WD but the exact same issues occurred with the second drive. Now if I plugged that same drive into my Hard drive dock and booted from the dock - not a problem Lion ran fine except obviously it was quite slow as a FireWire connection just isn't as fast as the one in the laptop also it is a little unpractical to have a laptop that needs a drive to be outside of the laptop to run. So thinking there is some huge compatibility issue with WD drives and Lion or my MBP (WD tech support mumbled something about Lion not working with their new drives) I went out and Bought a Seagate 750GB 7200 RPM Momentus drive. This was from a Mac specialist that claimed it would work fine in my MBP. Well it doesn't and this is where it all gets a bit weird. The drive worked for a few days just fine inside the laptop it was quick and did what I wanted to do but then 'crashed' when i restarted. I got it working again and then had to restart and this time it firmly refused to work. I re installed Lion and started up. After the initial chime the drive RANDOMLY showed the Apple Logo (normal boot up) then the folder with the question mark and then the broken signs (the circle with the line through it) and it cycled through them randomly for a few seconds (showing each for half a second) and then either stayed on the question mark or 'booted'. But when it 'booted' it did not as it took me to the Lion welcome screen which you get when you first install Lion. Which was even more strange. Also Now I tried repairing disk in disk utilities, I tried repairing permissions Nothing has worked so far. BUT again if I put the HDD into the dock it boots just fine. Someone please help me. What on earth am I doing wrong??? I have now spent £200 on HDD's and NOTHING has worked. It is confusing the hell out of me. HOW can these Hard drives not work. I also received another error once or twice right after the Apple Chime. 'Unable to find driver for this platform "acpi" - i can get the full error message if you guys think it is important. Please help me guys. I am literally giving up.