Help Fixing sd card... running into problems

[HikerMan]

Hi, I have had the problem where my HTC Desire can't mount the sd card, and am using the method whereby you open cmd and use 'fastboot oem enableqxdm 0' to fix it. I had done this before because it had annoyingly already happened... anyway, when it came to entering the line 'fastboot oem enableqxdm 0' it read '<waiting for device>' and stops there; the computer doesn't seem to be reading it at all. Am I missing any drivers? I have reinstalled and wiped windows since the first time I did this, so I will have lost everything I had, including programs, drivers etc. that may have read the device.
Please post any ideas you may have; if you need any more information about the device (I think this is more of a comuter related issue at the moment) please ask.
Thanks!