trying to run within WinXP

YES! ANSWER IS:- When you install Ubuntu as an application within the windows XP environment (portable or otherwise) NO!! thats correct you WONT see ubuntu from within XP itself. Why? its my understanding that Ubuntu only loads at start up as a duel boot system. Meaning that in XP your BOOT.INI file should have been modified and so when you reboot your machine once ubuntu is installed the boot menu should now offer you UBUNTU as well as XP.

NOTE: you can find the file boot.ini in the root directory of you drive C:\, you can edit the boot.ini file quite easily using notepad.

**If you only see the uninstaller from within XP control panel add/remove programs then it sounds like you installed Ubuntu correctly!. If the boot.ini file wasnt modified by the Ubuntu setup process that might explain why you dont see it & its not shown at start up either.

hope this might be helpful?

All files of Ubuntu are inside a virtual disk that Windows is unable to read. Allowing people to access this virtual disk and write on it could make this disk inconsistent, and unusable when booting to Ubuntu. The same way, you can't access a Windows partition when Windows was hibernated as some writing are in memory (exchange file).
I don't know if it exists a tool allowing to read a Wubi virtual disk in read only mode when Ubuntu was not hibernated.
I will assign this question to project Wubi, so our Wubi's expert (Mr bcbc) will answer you.

It sounds like the windows portion of the install completed but not the Ubuntu part. Right click on My Computer, Properties, Advanced, Startup & Recovery settings. Make sure the timeout is 15 or 30 and that Ubuntu is available in the drop down box to select the default OS (but leave Windows as the default after checking).