Hi Voltaire, welcome to the forum.
Please download and run the
Norton Removal Tool (from MajorGeeks) which should fix a lot of the problems, maybe all of them.
Norton can leave a lot of stuff behind when uninstalled.
After the tool has run, it may be necessary to repair the Avast installation. This is done via "add/remove programs" (I think it's "programs and settings>manage programs" in Vista. Find via the control panel.) Select Avast, then Change, then repair.
Avast does not have the facility to delete your temporary files. Try
Ccleaner (read the help file first; you can end up removing more than you may want removed) or
ATF Cleaner (also from MajorGeeks), or use the tools available in the OS, for disk cleanup. (A defrag once a month or so is a good idea, too.)
A lot of manufactured computers (and Dell is no exception) come pre-loaded with stuff you may neither want nor need. Check out
PCDecrapifier to help remove the bloat, and give yourself a bit more performance. Stuff starting with Windows when it doesn't need to is a major cause of poor performance.
A few of the programs that work well with Avast include Threatfire (behaviour blocker), MalwareBytesAntiMalware (demand scanner), Secunia PSI software inspector (Checks system for vulnerable/out of date software-Windows and 3rd party).
Actually, a lot of programs work well with Avast. It "plays" well with most other applications. (Except another Antivirus, of course.)
I'd also look at installing a
Hosts file (there are others available) and something like
Hostsman to easily manage it.
To improve protection, use a browser like Firefox with the NoScript add-on, or disable (or at least prompt) for scripting in all internet zones in IE. Nothing is ''totally covered". You'll be pretty good with those, though.
If the CD/DVD problems persist, please advise.