First, your Tivo has to be subcribed to the Tivo service and you'll need to go to your account at tivo.com. Under DVR preferences, next to the DVRs in your list, there should be boxes that say "allow transfers" and "enable video downloads". Click those boxes to check or uncheck them. You want them checked.
Once that is done, force your Tivo to call in to the Tivo service. After that is complete, restart the Tivo.
Look in the system information screen on the Tivo for a line called TivoToGo. If there is
a,a,a next to that line, you're golden.
Next, you'll need a Tivo wireless adapter or a compatible USB wired adapter.
http://support.tivo.com/app/answers/...er/r_id/100041
You'll have to setup a network between your Tivo and your PC.
http://support.tivo.com/app/answers/...up/r_id/100041
You'll need to download and install Tivo Desktop on your PC.
http://support.tivo.com/app/answers/...ns/r_id/100041
That should get you started.