Friend gave me an old PIII Dell laptop he had that was missing a hard drive.  It boots to BIOS ok.  I had an older HD I thought I could use, but turns out the connection is too small for the plug in on the computer.  Dell lists the hard drive specs as "ATA-5", but all new ones I can find are "ATA-6".  Will these plug in and work?  I know squat about laptops.  Dell wants 150 bucks for a 20GB ATA-5 HD, where I can get a new 40GB ATA-6 drive for 52 bucks at Newegg.  
Help?
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Looking at time frames, I have to assume ATA-5 is the laptop version of ATA-66, and ATA-6 is the equivalent of ATA-100?  I'm guessing.  Still no clue if the connections are the same though.