You could try using the drivers from Linksys's website here: Linksys by Cisco - WUSB54G Support
That said, I'm not sure that'll be of much use as the drivers for V1 are 6 years old. I'd be surprised if Windows 7 x64 drivers even exist for this old version of this device.
And.... it may be possible to rewrite the INF file using the hardware id string that is viewable in Device Manager by double-clicking the device, click the Details tab, select "hardware id", and manually type the hw id string that begins with "USB\VID" (1st./top line of text only) into notepad for use in editing the inf file (in the driver file). Replace the existing hardware id string (in the INF file) (if it's different than what the actual hardware id string is) with what ever you find in Device Manager.
I suspect the newer Version 4.0 would be required to work in Windows 7 x64. This is the actual download link for the V1 driver:
File size: 7.85 MB