hard drive upgrade and can't click on network


I recently got a new 80GB hard drive fitted by an apple centre and all seemed to be going smoothly but today I clicked on network and a terminal window and text edit opened. Weird. Now the apple centre is nearly 2 hours drive away and it'd be a bugger to have to drive all the way back. Can anyone here help?
When you click on my computer or the home icon The network icon no longer looks like it did (i.e. the grey world) but now looks like a text document.

I ran the fix it thing and repaired permissions (some of which were wrong) but it didn't fix the problem. I can see my Mac (an iBook) from the other Mac in the house when i use itunes or iphoto, but I can't use the network thing at all on my Mac.