Well, that was until today... because from now on, the "Rebuild All" doesn't run on my computer anymore... thanks to "Remote desktop connection"!
You can find this utility among the programs shipped with your Microsoft Windows XP PRO SP2 Operating System (and above):
Remote Desktop Connection allows you to connect to another computer using its address (IP or local network name):
If you want the other computer to work on your local data you may have to share your drive C:\
Warning: of course, you must trust your local network very very very much to do this! Or find another way...
Now, assuming that your computer's name is "\\MyComputer", you can make the second computer work on your data; just map the network drive using "Explorer > Tools > Map network drive":
And here you go... you can have an other processor doing the heavy tasks for you: