I've got a problem when trying to connect external WD 320GB 2.5" USB hard drive to my PC. When i connect it just nothing happens. No searching for drivers, no driver not found error and no new drive shown and etc. All pendrives work so i dunno whats the cause of this. In windows 7 it works as it should. I have nforce4 pro 2200 with all drivers installed but still device manager shows two unrecognised devices. Any ideas?

Check in Disk Management, does it appear there? Perhaps there's a conflict with drive letters or something.
Also, do the USB ports work at all? You mentioned two unrecognised deviced in DevMan - perhaps they're the USB root hubs. Have you tried other USB devices (storage or otherwise) in the same port?

do you have it connected to the front or the rear USB ports. some drives can only be sensed and workable by a USB 2.0 port even though they say its backwards compatible. I had the same thing goin on with my maxtor 750GB one. works not on the front ports but I gotta connect it to the back witch is a pain. (R1 and R2). also get the latest versions of your chipset drivers.

As i said before all pendrives work - i put them in the same port and they're fully working. And yes, i have the newest drivers.

Does your Win 7 run on another PC or on the same PC?
If on the same PC, then never mind.
If on another PC, then it might be a hardware issue with your MoBo (insufficient current of the USB power supply).

How are you powering the drive? A USB port gives 500mA, if I recall correctly, which isn't enough for a 320GB drive (even if it's a 2.5" drive).
Does the drive even spin up? If there's any lights on it, do they light up?

If it's working fine in Win7 on the same computer, then that rules out insufficient power as the cause, but I thought I'd check anyway.

Also, I ask again, does anything show up in Disk Management?
And have you tried searching for drivers for the two unrecognised devices? Bing their hardware ID's or something.

Its not a hardware problem guys. I have been using windows 7 before on the same machine and now i changed to R2 and everything works just fine but this external hdd. The power is ON cause power led is on and drive starts spinning and then stops as idling. Dont search for problems in my hardware config, its something about the R2 happening here.