Does mandriva recognise the usb wireless adapter as a wireless adapter or is it coming up as an unknown piece of hardware?
I'm not entirely sure about usb adapters but with wireless cards that linux doesn't have a native driver for you would need to use ndiswrapper to load the windows version of the driver into the kernel. It would be beneficial to read up on ndiswrapper.
Check you've got ndiswrapper - type
ndiswrapper at shell, if it can't find the command then you haven't got it installed, if this is the case then type
urpmi ndiswrapper at shell and follow the prompts.
Once it's installed, find the correct driver for your usb adapter, this will be on the CD you got with the usb adapter. You're looking for a .inf file which should have a .sys with the same name. You might need to do a bit of googling to find out which driver is the correct one as there may be several on your CD.
Have a look at this:
ndiswrapper
you won't need to do anything in the first CODE box because you will have already installed ndiswrapper. Start from number 2.
Hope this helps.