My USB printer is not recognized, and also a pen drive in the same USB port.
But when I put a usb to serial adapter, Windows recognizes it OK.
Of course the pen drive and printer works ok on my other laptop.
Are there any diagnostics that can point me in the correct (or any) direction.

First thing to do:

First, turn off your computer using Shut Down or pressing the power button and then UNPLUG it from the wall outlet. Let it sit for about a minute and then plug it back in.

Hope this helps someone fix that pesky “USB device not recognized” Windows error!

Tks for reply,
Have already switched off computer and didn't clear the fault.
Am on the verge of installing windows , but can not relate it to why my USB to serial adapter works ok. Would like to understand the fault by using a diagnostic to tell me more about the failure.

Did you install a driver for your USB/Serial adapter? Then before you reinstall XP and confront all that entails, why not try reinstalling the USB drivers? You could use your chipset driver cd that came with your system, or go to Device Manager, expand USB Serial Bus Controllers, and update drivers from the Microsoft website.

Maybe you can check your CMOS BIOS to see whether the USB port is enable. Just press the delete key upon power up before it read your OS. Some computer brand may use other key like F10 or F12. It will show on your screen when power up your computer. Once inside the CMOS check for USB setup. If it is disable than select to enable it. The other reason could be your drivers is corrupted and may need to use the CD to reinstall the drivers.