I'm not sure about Vista having it built in, but I know you could make a .bat with: shutdown -s -t 20 there, 20 is the time to shutdown in seconds, so change that to whatever you want.
Alternatively, look for something among the sidebar gadgets.
or change the number to however long you want in seconds.
save it as:
NameHere.bat
Job done. Double click to run.
If you want to know more things you can do with the shutdown command, bring up the command prompt and type 'shutdown' on its own. It won't shutdown your pc but it will give you a list of syntax you can add.
many thanx...it worked but now I am trying to set to hours/min and don't know how to do that ...you mentioned that I should type command shutdown , I typed it in run but I don't get a any list nor anything....but thanx again for your help much appreciated...