Forcing windows to send packets from one IP to another?

[Ref]

I need to force Windows to send packets that program wants to send to one IP to another IP, because the program (and whole system) sees wrong IP of this PC.
I remember reading few years ago about a Windows file in which you can do this, and the example which was shown was that you could simply write www.xsforum.org and it would open xtremesystems forum, just because in this file it was said that all the packets which should go to www.xsforum.org will go to the real address.

Do you know which file is it? Or do you know any program which does it?
I hope you get what I mean, and sorry for my english :(

[Ref]

does anyone have any information that could help me?

[NWEng]

You are probably thinking of the local host file, hosts, which is found in the C:\WINDOWS\system32\drivers\etc folder. It's a simple text file, just open and edit with notepad or wordpad.