Since you said that your computer is probably trying to hook up to your father's computer, this is what can be done:
First, right click on network neighborhood, then click on properties. You will see the different network interfaces that are installed on your computer. Choose the one that is being used ot connect to your father's cpu. Next, right click on that interface and then choose properties. You will see the different networking protocols and services that are being used. On the top should be Client for Microsoft Networks. Choose that and click on properties. You should see something about easy logon and stuff. Make sure you choose the option that says not to reconnect. That should help you.
There are other things that can make your system slow down. For example, if you're using WinXP, your computer might be set up to always check for new updates when you load up windows. Anyway, if you do have WinXP, I'd suggest you go to www.tweakxp.com
since they have some really good tips to help make your system perform better. Good luck.