It would be advantageous to periodically clear out your Temp files and folders, doing that before your scan could have saved you a lot of grief.
CCleaner - Temp File Cleaner, etc.The windows firewall XP firewall is usually good at keeping your ports stealthed (hidden) it provides no outbound protection and you should consider a third party firewall.
Any malware that manages to get past your defences will have free reign to connect to the internet to either download more of the same, pass your personal data (sensitive or otherwise, user names, passwords, keylogger retrieved data, etc.) or open a backdoor to your computer, so outbound protection is essential.
- There are many freeware firewalls such as, Comodo (care required now it is a suite not to install the anti-virus element), PCTools Firewall Plus, Jetico, etc. - Zone Alarm free works fine with avast and has a reasonably friendly user interface, however, the free version is becoming bloated with trial ware and is also crippled as far as outbound protection goes In the Program Control, configuration area, the slider will only goes as far as Medium protection, if you want more you have to buy the Pro version.
See A Forum discussion on free firewalls
http://forum.avast.com/index.php?topic=30808.0See
http://www.matousec.com/projects/firewall-challenge/results.php.
Personally I would stop it as it really shouldn't take this long. But we need a little more information about your system, RAM, CPU (intel core 2 duo, AMD 6400, etc.) your hard disk size and amount of data, etc.
Download CCleaner and run it to clear out the temp files. Schedule a boot-time scan as mentioned in my previous post above, hopefully that should be quicker and give you a head start.