Good resource for hacking computers would be Dan Brown books, or the movie Track Down featuring Kevin Mitnick as the hacker.

Physical hacking would be harder than over the internet, when it comes to covering your tracks. Using a bootcd that has a password remover would work great but how do you replace the password back to the original.

What would be more likely would be a home hack, maybe even wireless home hack if you want to add a little wardriving into the book. Alot of people bring there mail home with them, look at the VA issue a few months back good example. But hey I commend you for comeing here for help. Alot of writers would just make up a bullS*#t hack without doing the research. Those types of movies and books turn me off from reading them.

If you want to go with the wireless hack look at

wardriving tools

Netstumber used to find signals
Can antenna used to find location of wireless router
Look for WEP encryption tools
Packet capture tools
password brute force tools

the list can be long but if the person is not computer savy, you will find the wireless network is unsecure and the computer will have no firewall and filesharing enabled. I would use XP as the os that is getting attacked.

If you wanted to do a inhouse office attack, I would use a live cd like Kanotics that has NTFS support to pull off the hack.