The x50v has a 'Switcher Bar' installed in ROM. Check that out and see if it's to your liking. It doesn't offer the shortcut buttons, however.
If you're dead set on iTask, the creators of it have an app calle
GigaTask. You could give that a try. I've never tried it on WM2003SE, so I can't confirm if it works or not.
Also, search for HandyMenu and ... oh shoot, I forgot the other.
Also, I use
Tillanosoft's SmallMenuPlus for a cascading start menu. It also acts as a task manager if you like and includes a battery monitor on the title bar. (The non-plus version is free...)