OK, one point from your first post, rundll32.dll, I don't see it at all, much less more than once, see below.
I also don't see why there should be an exception for it in the windows firewall (something which provides zero outbound protection).
XP SP3 is the latest SP and you should consider updating as it also allows other things to be updated as well, browser, etc.
Try a clean reinstall.
Download the latest version of avast
http://www.avast.com/eng/download-avast-home.html and save it to your HDD, somewhere you can find it again. Use that when you reinstall.
Download the avast! Uninstall Utility,
find it here and save it to your HDD.
1. Now uninstall (using add remove programs, if you can't do that start from the next step), reboot.
2. run the avast! Uninstall Utility, reboot. If step 1 failed it may be necessary to run this from safe mode, once complete reboot into normal mode.
3. install the latest version, reboot.
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If you haven't already got this software (freeware), download, install, update and run it, preferably in safe mode and report the findings (it should product a log file).
1.
SUPERantispyware On-Demand only in free version.
2. MalwareBytes Anti-Malware freeware version
http://download.bleepingcomputer.com/malwarebytes/mbam-setup.exe, right click on the link and select Save As or Save File (As depending on your browser), save it to a location where you can find it easily later.
Both of these produce logs, run one, post the log before running the second and posting that log.
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