XP Pro does not recognize my USB HD!

[msanto]

Yes, but only 2 out of 4 systems, for some reason.

Here are details:

ARCDisk, USB 2.0 version.

Recognized by:

Clone PC, Windows XP Pro, USB 1.1 (P4 1.5 GHz)
Dell Dimension 8100, Windows XP Pro, USB 1.1 (P4 1.7 GHz)

Not recognized by:

Clone PC, Windows XP Pro, USB 2.0 (P4 3.0 GHz)
Alienware laptop, Windows XP Pro, USB 2.0 (P4 3.2 GHz)

All OSes have been updated. I noticed that the PCs that recognize the HD use USBSTOR.SYS as the driver, which is a Windows XP driver.

I even tried doing a repair of the OS ... no go ...

Have tried the HD direct (no hub), powered up, with external PS (says it does not usually need it), without external PS. No luck.

Any ideas?

And yes, I've tried the driver disk. It says that none of the drivers on the disk apply. I think they are all 98 drivers.

Help!