USB WiFi Not Connected Unless Logged In

I have an Edimax EW-7318USg (USB) WiFi adaptor plugged into a Windows Vista PC. All is fine when someone is logged into the machine, but otherwise it remains resolutely disconnected from the LAN and the services provided by the PC (Windows file sharing and a database server) are consequently unavailable. I have unchecked the option that allows Windows to shut down the network adaptor to save power (and rebooted the PC, just in case), but it made no difference. Other options did not seem relevant. I've also been Googling for about an hour now and found nothing else to try.

Can anyone tell me please how I get the adaptor to remain connected to the LAN? Is it a failing of this particular USB WiFi adaptor (it's the only one I have, so I have means of comparison)?

 

Thank you, TonyT! I removed the supplied software and let Windows find it's own driver off the internet (with the aid of a long TP LAN cable), and now the PC is connected to the LAN when no-one is logged in.

I didn't find any setting that implied that it needed to be selected or unselected to maintain the connection except the Windows power options, which I had already tried before my OP. It's a pity I had to remove the supplied software as it gave much more information about the signal than does Windows. If I get the time I'll explore this further.