My computer is acting up after installing avast

[Aralhach]

Well, I haven't been around for a while.  I recently uninstalled NOD32 Antivirus System (from ESET, time's up) and decided to continue protection with avast!

I've got:
Windows XP Home Edition SP2
Pentium 4 HT
512 MB RAM

I installed the 4.7 version (I had that) and then remembered that I had heard something about a new version.  I right-clicked on the avast! icon on the taskbar, and opened the antivirus.  It took FOREVER to load.  Then I clicked on the menu and clicked on "Program update", and it did NOTHING AT ALL.  So I went to avast.com and started downloading the installer.

In the middle of the download, avast finally popped up the green window saying "New version available, click here..." but since I was downloading, I ignored it.

When I finished the download, I double-clicked it.  It said update, so I selected that.  Then I restarted, and my computer started acting weird.  I tried to watch a trailer on Internet (with Mozilla Firefox) and the thing locked up on me.  I thought, OK, I'll uninstall and then do a clean install.  But there was NO UNINSTALL OPTION IN THE START MENU.  So I went to the Control Panel, and it just sits there with the icon on the flashlight searching.  I had to go into safe mode to uninstall it, and reinstall it, but something is still wrong.

As I am writing this, my taskbar just disappeared, I'm kinda starting to freak out.  This didn't happen last time I tried to use it!  Is it that unstable now?
Do I have a virus?  My control panel  still has the same problems, and nothing is working right. HEELP! Please!!

[Lisandro]

I suggest an installation from the scratch:

1. Uninstall avast from Control Panel first.
2. Boot.
3. Download the latest version of Avast Uninstall and use it for complete uninstallation.
4. Boot.
5. Install again the latest avast! version.
6. Boot.
7. Check and post the results.

[Aralhach]

First of all, sorry for freaking out.
I was unable to uninstall avast! from the Control Panel, it wouldn't even load!

Now, I was able to solve the problem.  Every time I powered up the antivirus (the "Start avast! antivirus" option) it scanned the memory until it reached the "sens.dll" file.  I managed to use the System Restore to boot up better and scheduled a boot-scan.  "sens.dll" was infected with a Trojan (I can't remember the name, forgot to write it down).  Anyway, I'd like to congratulate ALWIL for their great work in programming this antivirus (great idea, the boot-scan thing).  However, I do have some suggestions:
1.  I still wonder why the real-time scanner didn't catch the infection.
2.  It would be nice if this uninstall utility was available from the start menu, and not as an external downloadable package.

This trojan also kept me from executing the installer (to try to reinstall again without uninstalling - the Control Panel just sat there with the flashlight thing). It said that the last action was Spawning or something like that.

Any tips from you will be more than welcome.
Thank you again!

[rassel]

Now, I was able to solve the problem.  Every time I powered up the antivirus (the "Start avast! antivirus" option) it scanned the memory until it reached the "sens.dll" file.  I managed to use the System Restore to boot up better and scheduled a boot-scan.  "sens.dll" was infected with a Trojan (I can't remember the name, forgot to write it down).

It is bad if the virus infected in your system32 folder or in your most important part of your system.

I tried before and it killing my laptop so i did a boot scan everything fine.