Gettin' way too deep in here guys.
Sounds like she doesn't want to get into any networking or sharing or any of that, just wants to make a copy of the Calibre library and put it on a different computer.
yasmeen57, I was kinda wanting to test this myself, so I just did it. I have my desktop and an netbook both running windows xp. Here's what I did.
Install the same version of Calibre on the Netbook (0.6.18 in this case). Then you want to copy your calibre library to the new machine(netbook). The calibre library is generally located in your user area (e.g. C:\Documents and Settings\Kenny\Calibre Library). You can check this by looking in Calibre under "Preferences" - the first entry under General will show you where the library is located. Copy this entire directory and put it in place of the default library on the new machine (copy it and change the location of the library in the new computer if you prefer - there is a browse button next to the url in the preferences) once you set it, click 'OK' and you're done.
Of course as I'm sure you know any changes made on each machine from that point forward will be for that machine only.
Hope that makes sense. If not, just ask.