On the Dell Precision 690 driver support page I could not see Windows 7 64bit. This leads me to the comclusion that the operating system you are trying to install is not compatible. See here
http://www.dell.com/support/drivers/us/en/04/Product/precision-690
So you would use either the highest supported version of Windows, namely Vista, or try to find driver(s) elsewhere. No one would guarant that you succeed in this incompatible configuration. Install on bare computer without any external device.
Regards
Milos