Do the KB and mouse show up in the Device Manager? If they're not working there should be yellow !'s on the icon.

If you know parts of the following please ignore, but here's how to check the driver files manually. Of course you'll need the Mac KB & mouse to do the navigating...

Right click 'My Computer'.
Choose 'Properties'
Select the 'Hardware' tab
Click the 'Device Manager' button
Click the + next to 'Keyboards'. There should be one entry.
Right click this entry and choose 'Properties'
Select the second tab, 'Driver'
Click 'Driver Details'.

What files do you see (if any)? My standard Dell 101 key k/b has the following files listed for it, both from M$
C:\WINNT\System32\DRIVERS\i8042prt.sys
C:\WINNT\System32\DRIVERS\kbdclass.sys

Click OK.
Now since I don't know where a keyboard .inf file would be I can't help past this. I have attached the two .sys files referenced above, in case they've been deleted from your machine. I also found a (somewhat) relevant M$ KB article here: http://support.microsoft.com/default.aspx?scid=kb;en-us;Q255151

I hope this is a little helpful.
-Zeke