Taskbar doesn't work right.

Hi Mordido;

Deleting the hp\137903\Program\BackWeb-137903.exe definitely did not cause your problem. Leave that deleted.

Im not so sure about C:\Windows\ALCXMNTR.exe since according to this link
http://startup.iamnotageek.com/srch-AlcxMonitor.html
it has something to do with AC97 Audio and you cant adjust the volume from the sytem tray. But for the time being lets assume you can live without this registry entry and that is is spyware.. so good riddens.

What happens if you right click on the task bar and choose properties.
In the Task Bar and Start menu properties box click the customize button
What does it say in the behavior column??? Set it to Always show.
If it is already set that way then set it to hide when inactive.
Ok your way out. Go back in and set it to always show. Ok your way back out?
If it doesnt show, try rebooting to see if it will show back up.

If that doesnt work you may want to try unchecking the Hide inactive icons and see if it shows up then.

I had a problem after installing microsofts newest patches with my Local area Network icon not showing up, then a day and a half latter it was back again. Realy strange stuff.
Let me know how you make out

Dont know if senad's tip will work but make sure you backup your registry before you try it. Just in case.

you could safely run a system restore if it is enablled, or go to the post screen and choose last good known config. You can also run sfc /scannow
type that in the run button, you will need your windows xp cd. This will restore the integrety of your system files which by the way could prevent certain programs from running properly if corrupted or changed.
When you explore the sounds and audio devices in control panel> firstly do you windows xp sounds check any audio commands eg exit windows has a sound next to it, is it greyed out or can you play the tester?
Have a look at your audio part and what driver is in there you could be using the wrong driver use that little scroll bar and make sure it points to the correct drivers check which drivers being used in midi music, once they are correct check the use only default drivers.

When you first open sounds and audio devices have checked the show vol icon on the toolbar.
You can also try installing this windowsxp tweakui which has an in built repair icon cache option.
Microsoft PowerToys for Windows XP
http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx

http://www.totalidea.com/tweakxpdown.php
Try searching for  .*mid  using the search and see if you can find them okay if they become damaged in someway especially removing any programs that may have taken ownership of them your audio will not function correctly.

Check your event viewer from control panel administrative tools>applications> event viewer.

Run a dxdiag and see if there is any problems with your audio etc. From start run type in dxdiag
Using your mainboard cd that came with your computer re-install all your drivers.

In system devices are there any yellow question marks?

check > start> all programs>accessories>system tools>system information>components> problem devices? Or check the sound devices.

Have you tried also rightclicking the toolbar and add quick launch or taskbar  toolbars show desktop.This will add a link.
If the previous programs have changed at all check that are still running at start up these programs usually show up on the rightside of the taskbar when running.You may have to re-install some.
Hopefully these will restore you back to your originals. :)