From doing a quick search you'll have to get the model number of the PC, as there's a few different mothods, some are pressing `R' on boot-up, pressing F8 on boot-up and others are does insert disk and select boot from DVD when prompted.
Here's the list of Advent PC's:
http://www.uktsupport.co.uk/advent/pc/model2.htm. I would suggest printing out the instructions for your model #, just in case you need to look over it again. Plus no going back once you've started the process, it will restore the PC to the same settings that where applied at the time you made the restore disks.
Are you connected to the router using a wired or wireless connection.
Wired it should work straight away.
Wireless, you made have to install the correct drivers/software that came with the wireless adapter. Then it's just a case of selecting your network and entering the correct passcode.
If you've added any new additional peripheral devices, Printers, scanners, Mice, etc you may need the drivers/software for them as well. If you have peripherals that need additional drivers/software go to the manufactures website and get the latest versions.
Q. what software are you using for email. There made be an easy way to export your setting, emails and address book. So you can import them back after you've done the system restore.
---------- Post added at 20:28 ---------- Previous post was at 20:24 ----------
Forgot, you may want to download Belarc Advise (
http://www.belarc.com/free_download.html). run the software and it will give you a list of all the current hardware, software, driver version etc on your PC which you should save or print out. So if you do encounter any problems it might help you solve them more quickly.