FWIW, when I borked the printer drivers on this X21, it took about 5 minutes to fix, not counting reboots (which didn't fix anything. I didn't do a reboot when I actually did what fixed it, but I recommended one for you because it often makes things work better...)
I'd say about 10 minutes if you don't do the reboots, 20 if you do (depends on how long your T21 takes to boot).
Also, these directions are for Windows 2000, and will also apply to XP. If you're running 95, 98, or ME, then they may not work as well, but try to apply them as best you can. Also, on those OSes, you will HAVE to reboot when my guide says to reboot, IIRC.
TP T61p | It doesn't actually have a type-model any more... hacked in ALL the mods! | 15.0" 4:3 chassis, QXGA, T9500, 8 GiB RAM, 750 GB HDD, Win7 Pro, Advanced Dock, PCIe QFX 570