@ OP: May be try to use the searching tool for Avast on your fresh swiped & re-installed XP system if you can't find it with the Add and Remove Programs in Control Centre, where you could uninstall it, if you do indeed have it somehow still on your system. This though, you are seemingly to be saying that you have done! Personally I don't understand how this is possible unless there are other factors or circumstances involved like if you've not actually swiped the hard drive, have more hard drives or partitions or a former or new raid array containing or re-installing Avast (or partly thereof) or even an off line back up or whatever but some such caveat. You also say you were having problems with your system, may be you also have some malicious trouble perhaps? Make sure that when you re-install you unplug your system from the net - cleanly reinstall XP and a few programs, especially security applications before you then physically reconnect to the web.
OK, now my own problem, while I've used Avast!5 mostly as my resident free AV since it came out in a multi-facetted security set up. (I tried the previously jukebox versions, but I never liked it although I very occasionally used it as a back up on-demand AV scanner.) Until Avast!5 I primarily use AVG Free as resident or else Avira AntiVir Free, together with Avast I refer to these free AVs as the "3 A's" of free AVs and I switch between which is best as resident, but also have the other two on as on-demand scanner back-ups, I have started using BitDefender 10 free for this as well as the forth. (I've tried Comodo AV free & MSE which make both XP and W7 really lag terribly and I can't set them to on-demand only while Comodo isn't purposely designed that way according to their philosophy anyway and I really don't like PC Tool's or Trend Micro Free AVs.)I use Windows Firewall or else Online Armour Free FW on either XP or W7 and of course I use multiple free Anti-Malware/Spyware programs such as Hitman Pro 3.5 Free (for scanning only, but not cleaning), Lavasoft Ad-Aware Free (resident), Emsisoft a-squared, Malwarebyte's, Spybot Search & Destroy (Scanning only), Spyware Terminator (Scanning only), SpywareBlaster and Webroot Spy Sweeper... (I've tried SAS, but unless you pay for it it becomes a Trojen IME, also PC Tool's Threatfire, but it seems too much like scareware to me with pop-up adds and I use CCleaner freely.
I sometimes trial Paid AV/ASs as well! No I did have a lagging system with all that on there or too many running processes, because I only have one resident AV,FW and AM/AS running and I only scan with one at a time. My rationale is obviously a (admittedly many) multiple approached with residents and on-demand back-ups and as varied sourced rather than a single approach kind especially prevalent of the Paid Full Suite variety.
Anyway I had to clean an unprotected 4 year old HP XP PC of a relatives recently primarily because IE was no longer functioning and since that was the only installed Web browser it couldn't connect to the net! I used a USB stick to back up the files and another I filled up with other browsers and all of the above security programs to clean the machine. I had to use this approach because it was a bought out former work computer that the IT guy didn't provide either the HP/mobo disks or XP and I didn't have another spare to swipe the HDD and re-install XP. XP booted quick and the system didn't lag but IE wasn't working and WD and DEP alerts were both frequently popping up.
While I cleaned the infected system and installed many of the security programs in a like set up to mine for protection and Firefox as a safer alternative to the hijacked IE7, which I completely uninstalled and replaced with IE8 afterwards. However, some programs with self extracting aspects as part of their installation procedure, although not all, wouldn't install because that self extraction wouldn't happen because of some of the damage to the XP OS that the bad stuff had done. One was Avast!5, but also BitDefender 10 Free and Eset NOD32 AV/AS I tried to install as a free time-limited trial. The only things on there were the laggy MSE, Avira and MBAM, there were fours year out of date Spybot S&D and unregistered (unpaid and non-cleaning) Spyse, which I used first before sticking the security USB stick in which found nothing much, SS&D cleaned just 2 items! Even After I removed them, MSE (which was the fist I managed to actually get to install, scanned with it first, which cleaned a bit off, but Avira found way more afterwards!) and later I uninstalled Avira as well, but I couldn't get these 3 programs to install, not even later when it was cleaned. In the end I left AVG as resident on that machine with Avira as the only AV on-demand back up out of my usual foursome, but I really wanted to put Avast!5 on as resident. I'll try Avast!6, but I expect the same non-self-extraction issue to occur.
My question is what is the self extraction aspect to Avast!5 (and may be 6) that is possibly similar to both BitDefender 10 Free and Eset NOD32 AV/AS that could be prevented by virus or malware damage to an up-to-date (SP3) XP Pro OS and how might I repair that to be able to install Avast and by extension over programs with a self extraction aspect to the installation procedure? (Consider that other applications with self extraction aspects did install on that system, before I tried these 3 again and I have checked them by actually installing them back on my W7 32 PC from the USB stick.)
Sorry for them long post, but I hope this detailed explanation is interesting to someone, cheers.
