Put antimalwarebytes on a memory stick and run it from there.
Download hijackthis from: http://free.antivirus.com/hijackthis/ and run it and post the log here.
I'd install, update and run Malwarebytes now before you do anything else.... you will need to give it net access to update, but don't need to open any browser windows, then restart and see how the add/remove goes. Can you run programs on the laptop? just try a few and see....
There's a Norton Removal Tool you can use to uninstall Norton without using add/remove - probably best use this anyway as it always works 100%, then you can install Avast.
Check the XP system files by going to start > run then typing sfc /scannow in the box... this will take a while, but will check the validity of the system files and replace any corrupted or missing. You might need the CD for this....
Try Microsoft Security Essentials against Avast. I used to have Avast on my WindowsXP home edition then avast went on to their 2011 version and it didn't work.
Their are also a lot of "false" viruses out their which starts bringing up hundreds of viruses so called and then they say its only their program will fix the problem. This is to get you to buy it, often system restore will put you back on track.
An easy but serious program is System Mechanic which I use occassionally if I land up with problems unable to overcome worth checking out .
You can remove Norton another way here is the walk through
go to- my computer right click - right click on open- right click on local disk (c)-right click on open- look for program files and right click on it-right click on open and you will get a load of boxes come up.
Find Norton and right click and go on the drop down list to delete. That will get rid of Norton for you. You may have to remove the short cut icon on the startup page as well as it is now redundant
Alternatively go to search - files and folders--all files and folders- type in Norton then search. This will bring up everything to do with Norton and delete whats on the list, have to say here you may be prevented from deleting every line so try the method I outlined first
Black I didn't say open control panel go to the my computer icon on the startup screen then follow the walk through. This should work
Realspeed
Looks like the XP exe problem - you can get a registry fix for it that I uploaded for you here. Just download, right-click it, then select merge or install from the pop up menu and try running a couple of programs again....
While I'm a little biased here, being a helper at one of the tech forums listed, if you are getting redirects, and messed up file associations it would be best for someone to look over your pc in more detail.
Posting on a specialist forum where a trained helper can look over your computer is usually the best way of making sure all traces of malware are gone. Entirely up to you, but it's free specialist help if you want it.
(On the basis all of these sites offer free help and are all non commercial, pretty sure it's ok to post them - can't see anything in the rules against it.)
The following sites are part of Unite and offer expert help:
http://forums.techguy.org/
http://www.bleepingcomputer.com/forums/
http://www.techsupportforum.com/forums/
http://www.geekstogo.com/forum/
http://forums.whatthetech.com/index.php?act=idx
who says there arent professionals here?