Under most circumstances, drivers are placed in WINNTSystem32Drivers. However, the programmer who wrote the installer INF script could have put it anywhere. Sometimes they end up directly in WINNTSystem32. Occasionally you'll find one in WINNTINF.
The real question in your case isn't so much where to find the driver but how to get it reinstalled. The installation scripts generally copy themselves into WINNTINF but this is not always the case.
You can't just make a copy of INF and DRIVERS because that won't preserve the registry settings. That also might not get the filter drivers, if any.
You might want to take a snapshot of the SYS drivers that are currently in memory, figure out which ones are third-party drivers, then track down the vendor's web site to get the full installation package.
The PSTAT utility from the Resource Kit is the easiest way to get a list of the SYS drivers.
This was first published in April 2001