If you don't have XP SP2 and don't *want* XP SP2 (for whatever reason), you'll have a problem using the FX1 in HDV mode - the PC will want drivers for a "AV/C Subunit" device that don't seem to exist, and alas the camera will be unusable.
Now, this is NOT the same problem as the missing "AV/C Subunit" drivers for SD cameras that you'll find when searching the net (involving renaming a msdv.inf.1 file back to msdv.inf). In this case, it's because the system doesn't know what to do with a HD tape source.
Above WeWerk thoughtfully says to install the Sony D-VHS Tape device - and it took me a couple minutes to figure out how.
After you've plugged in the camera and cancelled out of installing "AV/C Subunit" drivers, go to the Device Manager where you'll see an expanded device of the same name with an yellow exclemation point. Right-click on that, select UPDATE DRIVER, select INSTALL FROM A LIST OR SPECIFIC LOCATION, click NEXT, select DON'T SEARCH, click NEXT, select the "SOUND, VIDEO AND GAME CONTROLLER" category, click NEXT, scroll down to the SONY brand name, then select the "Sony D-VHS Device".
After installing this the camera works perfectly!