Avast is a good antivirus, I use it myself, If downloaded from the Avast site it shouldn't be a problem.

You need to use the correct tool to uninstall it properly here

What were the other tools?

Restore XP

Boot to the command prompt and type:

%systemroot%\system32\restore\rstrui.exe

Press Enter and follow the on-screen prompts to restore to an earlier date/time

if will not boot to command prompt then:

Restore from recovery console http://www.myfixes.com/articles/system

boot from the XP CD. Start Windows Setup and press R to access the recovery console. Select your Windows installation, then type the administrator password – press Enter if there isn't one. Now enter the following commands:

CD C:\ CD "system volume information_resto~1" DIR

You'll see a list of restore point folders with names such as RP1, RP2 and so on. Pick the restore point you wish to use, using the folder date stamps to guide you. Enter the commands:

CD RPx (the restore point you chose) CD SNAPSHOT

This takes you into the folder containing the restore point snapshot files. Copy the Registry backups so that they overwrite the existing Registry files.

COPY Registrymachine_system C:\Windows\System32\Config\System COPY Registrymachine_software C:\Windows\System32\Config\Software COPY Registrymachine_sam C:\Windows\System32\Config\Sam COPY Registrymachine_security C:\Windows\System32\Config\Security COPY Registryuser_.default C:\Windows\System32\Config\Default

Type the command exit to close the Recovery Console and restart the PC.

The above is to get it to restore without losing anything

if you have everything you need backed up then you could try:

HP/Compaq laptops. 1. Reboot, and repeatedly press F10 (F11) at the HP logo until the recovery screen appears. 2. When the recovery screen appears, press "Next" and then "Yes" to perform a non-destructive recovery. 3. To perform a destructive recovery, click "Advanced" and then "Yes". 4. After the recovery is finished, the laptop will reboot.