after booting board not recognized

Topic: after booting, board not recognized

OS Windows XP Board: Nano w/ Atmega328 IDE Arduino version 0021

Uploading worked fine with COM3, using the latest FTDI drivers. However, after simply booting the PC :

(1) on USB plugin the board is not recognized: "USB-device unknown" (2) in the hardware manager only COM1 shows up, COM3 is lost. (3) the FTDI drivers for reconfiguring the "unknown device" to COM3 cannot be found. (4) uploading not possible What can be done?

(verbose details in my next message)