sounds like you have a major e-mail problem. First thing I would suggest is disconnecting your internet connection, then try to run Norton if it will run or find what it's suppose to. I won't get into why I don't suggest even having Norton as it won't help your problem. From what you describe, it sounds like you had some mass e-mail worm and it's probably through your Outlook Express. If you unplug your internet connection, your mail should stop flow. It also sounds like you had issues before Norton, don't know what you were running before if anything.
ASSUMING YOU CAN GET WINDOWS TO WORK:
Backing up can be a task in more than one way. If you pc is infected, you may have a hard time getting anything to work, plus if you don't know where the viruses\trojans and who knows what else, is on your system you risk backing the infection up without knowing it. This is why I think you should do the above mentioned before anything. I can almost guarantee your pc is infected and don't know if it's in the system restore or not. If it is, we'll find out soon enough when scanning if unable to delete from it's directory in which case sys restore will have to be set to 0% and shut off and you won't have a restore point. If bad enough you may have to reinstall the system.
If you can , I believe Norton has right click virus scan ability. Select your most important files\folders that you don't want to lose and do a virus scan on them. If they are clean, back up to CD\DVD if possible. Or if you have another partition that's not holding infected files.
ASSUMING YOU CAN'T:
Since you have XP home, I would also assume OEM as you didn't specify. What I mean is did XP home come with your pc pre-installed or did you buy it yourself? You didn't say what brand of pc you have either, RAM , hard disk, etc...
There are a number of possiblilities for a reinstall of the OS depending if you answer the above. One step at a time though.
Note: This is a hard lesson to learn if you don't back up your files regularly.
i'm running windows xp home edition on my computer,i have a bt broadband connection that came free with norton anti virus software.all day i have been getting symantec messages saying that my emails cant be sent(dont know which ones coz i havent sent any)but it says there was something like 540 of them.anyway scanned my computer,said i had to install symantec live update,did so then all of a sudden all these worm and trojan warnings were coming up and now my computer has stopped working at all,gets to the windows screen but then cant do anything,also been having buffer overrun messages for a day or so,tried reinstalling my windows xp but that hasnt resolved anything..the email messages just kept covering the screen.i dont know how to reformat,what would i have to back up and how?now that i cant get anything to work properly.could i just be getting conflicts in my computer(ie i have a downloaded driver(geforce mx4000) for my graphics card,using a soundblaster x-fi soundcard any help would be appreciated