Latitude 13 Windows 7 Slow

I have two Dell Latitude 13 laptops in my possession, both with the same problem. They suddenly started running very very slow. Trying a clean install of Windows 7 was futile, even the installer was running so slow that it took 20 hours on one computer. All of the hardware checked out and Windows XP worked just fine. I sent one to Dell and they sent it back to me claiming there was nothing wrong. I'm not sure what happened to these laptops, but the fix was to go into the BIOS and change the SATA controller from AHCI to ATA. After that Windows 7 installed normally.

UPDATE:

This seems to be the result of the ribbon cable going bad. The first sign is the issue I've described above, but eventually as the cable degrades further, it will stop being able to read any hard drives at all.

From the form post here:

Put the original drive (or another sata drive) back in & see if it works. If not, it's likely a failure of the ribbon cable from the mainboard to the daughterboard that carries the audio & sata ports.

We bought 100 of these units last year & in six months had a 73% failure rate. 87% of the failures (63% overall) were due to that cable failing. It is a known issue that is still recurring. The whole fleet has had the cable replaced twice, some more than that, but several of the replacement cables have failed also.

I would suggest you replace the original drive & have it addressed under warranty. If the machine is out of warranty, lean on them because it is a known issue.

In fairness, I will say that Dell have been very supportive through our troubles, & have worked hard to address the issue for us.