Just thought I'd let people know that I was able to get rid of the annoying 'installing' problem when the phone is starting up, without reformatting the memory card. First you must go into the app manager and make a note of the .sis files eg; something like a000017c.sis, that you can't delete in the app manager. Then put your memory card in a memory card reader and go to the folder private/10202dce and delete the sis files you couldn't remove. Then put your card back in the phone and bob's your uncle, no more 'installing' message!
Remove 'installing' message from startup
if you dont have a card reader it can be tricky as it generally doesnt allow you to use the phone in mass storage mode when its been silly like this (says memory card in use). You can get it to connect if you are quick or last time I did it this way:
-took memory card out
-pluged in datacable
-select mass storage, click ok
-put card in
then it should (hopefully) connect as mass storage before it realizes it has uninstalled apps etc.
-it would have been a lot easier if nokia hadn�t got rid of the safe mode (option to boot with no apps) when they went to s60v3!