restore does not erase your files, but it will take out software changes that may have affected the system, like installing avaira.
You should look and see how far back the restore options go, it varies.
Don't ever install software that claims it will fix, repair, speed up or clean your computer. 99% of it is a scam. You are warned!
The best way to repair an XP computer is with the XP installation disk, use manufacturer supplied resources only. Don't be fooled by scam software downloads.
The best way to protect a computer is with all in one, subscription, security applications such as Norton 360 or Panda Internet Security. Loading multiple security solutions from the internet often causes conflicts and problems, or a complete system crash and loss of data.
Back up all your personal files to CD, DVD, online backup service such as Mozy, before trying any repairs. This is most important.
If Avira and Nero are causing problems, try deleting them after you have backed up your personal files. Do you know how to do this?
You can re-install Nero later, after the problem is resolved.