Well, you could invest in another seat in front of your computer, or you could google "Free remote control software"
The first is a hardware solution and requires no software, whilst the second is a software solution and requires no additional hardware (assuming that you and your friends are on a LAN, WAN or the Internet)
Hi, if you mean you want people to be able to see your screen and take control of your computer if you have a problem then there is a fantastic free service called logmein. the website is www.logmein.com. I could not praise it enough, I put it on all of my customers computers and I can take control if they are in trouble or are unsure.
XP includes Remote Assistance which provides this very service without the need of third party software.
Go to Start/Help and Assistance and type in Remote Assistance and you will be presented with a couple of options.
Choose whichever suits.
If you're prepared to pay a small fee and it's a bit of a one-off thing and you don't want any hassle installing stuff and setting software up, then I can recommend Copilot: