Time

Hello, Is there a way to have php run a script at a certain time? What I really need is something like cron on unix systems. I would use windows scheduler but it only goes by days. I ned to run this once every hour. P.S. To let everyone how helped me before. I can now send commands to an outside program I am running w/ the fsockopen command. This is after I open the prog. with popen. Thank you all for your help., especially Steph and Micheal. Your efffort and advice is much appriciated. If your ever in Athens Ohio the first round is on me :-)