External drive CRC errors

Hi everybody

On january, I ordered an external harddrive on Ebay which has a SATA 120GB Seagate drive. When I received it, I copied all my files as I'm going to use it as a backup storage, and when I wanted to install AutoCAD 2008 from that drive, it failed because of CRC errors.

I sent the drive back for repairs. Although they didn't find any problem, the replaced the drive inside and when I received the new one, I had the same problem.

First thing I did is to put the AutoCAD installation file (a 800MB zip file) on a USB pen and try to install from there. It was a success. Then I switched my intrenal drive of my laptop with the one I bought and installed Windows XP, copied the AutoCAD file on the drive and also installed it. Still working. So I left the installation file on it, switched the drives back, and tried to install it and the errors were back.

This morning, I had the idea to plug my external drive to my mom's computer and also try the installation of AutoCAD on it. Guess what ? No error !

So it really looks like there is a reading problem with my laptop, an Inspiron 1501 with a Sempron 3500+.

I found on the Internet that CRC errors usually happens when there is a bad RAM in the computer. A year ago, I added a Kingston 1GB I bought at FutureShop (http://www.futureshop.ca/catalog/proddetail.asp?logon=&langid=FR&sku_id=0665000FS10087541). So I ran Memtest86+ from a Ubuntu CD I have for a couple of passes and no errors were reported so far. I also tried the AutoCAD installation with one of the two RAM stick at the time in each one of the slot and the four tries failed. Looks like its not a memory problem...

Knowing my BIOS is up-to-date (2.6.4 rev A16) and I have all the latest drivers from the Dell Support site and the latest release of the ATI drivers from their website, can it be a BIOS or drivers problem ? Should I try to downgrade the BIOS (which version?) ? Is there a problem with my USB ports (although I never had such problem before in almost 3 years) ?

Please lighthen me !

Thanks in advance.