I have a Fujitsu Lifebook Model T1010 which is a touchscreen laptop currently running on windows vista. I also had the same problem with the green volume indicator bar. It was working fine, then one day, while I was adjusting the volume, I noticed the green indicator bar was gone. I became saddened by the idea of having to look at the little volume icon in the taskbar every time I wanted to see where my volume was set at. I called Fujitsu customer support expecting a quick and easy solution, however it wasn't helpful one bit due to the fact that the Middle Eastern customer service reps didnt understand me at all. :SIGH:.. Anyway, after receiving useless information and hanging up with Fujitsu customer support, I did futher research into my computer and fixed it myself! This is what I did: Opened my Computer folder>Local Disk (C)>Program Files>Fujitsu>Fujitsu Hotkey Utility>then there it was.. IndicatorUty. It's an application, and when I opened it up.. BAM! My good ol' green volume indicator bar came back! Must say, I was happier than an 8 year old child on Christmas morning =D
So, here's what we should try with yours..
Since you're running on windows XP, it's going to be a little different, but we'll just wing it ;D
1) Open your "Computer" or "My Computer" folder
2) Open Local Disk "C:", and navigate to "Program Files"
3) Search for a folder labeled "HP" or something similar that would contain files and applications of your computer's manufacturer. In your case, this would be "HP"
4) After locating and opening that folder, search for a folder labeled something along the lines of "HP Hotkey Utility" Note: If you can't find a folder named "HP Hotkey Utility" you will have to open each folder one by one and search for the "IndicatorUty" (indicator utility which will bring back your precious green bar) This is an APPLICATION and SHOULD have a little green "splat" looking icon associated with it.
5) Once you have located this application, simply open it, and presto! Adjust your volume and you should have your little green bar back!
I hope this helped! Let me know how it goes...