Computer Trying to Logon to Nonexistant Network

My problem is that in the past I tried to set up a home network on our home PC's without success. I abandonned the project and for a long time just used the PC's standalone with no problems. Somehow my wife's computer was changed to where it is now attempting to log onto a network that does not exist. How do I tell it that there is no longer a network available and it should run as a standalone PC? I have a Utility that allows me to log onto the PC and run in a DOS environment, but I want to enable her Windows Desktop so I can have my laptop back. She is running Windows XP Home edition.

 

you are not clear enough please
" so i can get my laptop back "
Is the laptop with a wireless card trying to log onto a wireless network?
If so there are a number of switches / options in the wireless networking card advanced options
One is to "log onto non preferred networks "
Uncheck this
Delete any of the extra networks seen in the scan networks area
If encryption is not turned on in your router ( wireless)
You can turn on encryption in the router and set it so it will only log onto that encrypted signal

 

Sorry to be confusing. The problem PC is a desktop ( Sony Vaio ) the reference to the laptop is because she took my laptop until her pc is fixed.