How to prevent a software from accessing the internet?

[spi]

Hi,
How can I prevent a software (installed in my computer) from accessing the internet?
Without firewall is it possible?
which is a free  firewall? ( I like the style in Bitdefender..which will prompt you that XYZ is trying to access the internet allow/deny?) .But since Bitdefender is paid software...I can't afford it.
Any similar software? OR any setting in XP that will block the internet access to the software.

Thanks in advance

[Carbon Dudeoxide]

You should be able to deny a program access to the internet using the Windows Firewall.

What Operating System are you using?

[spi]

Hi, I am using windows XP

Please tell me step by step method to do so.

Thanks

[drmsucks]

This has a good reputation: http://www.personalfirewall.comodo.com/

Make sure that you get the free version. If you get it, be sure to disable the firewall in XP.

[CBMatt]

I second Comodo.  It's a lot easier and much more effective.