Applications Cannot Open

[kwabena]

hello,
i'm helping a friend with her 15" powerbook g4 mac os 10.5.
the problem is i cannot open safari, disk utility, yahoo messenger and the list goes on.
i already downloaded mac os 10.11 on my powerbook. but, i cant seem to install that either.
geeks, what do you think is the problem? thanks

 

[bartelby]

Have you tried repairing permissions and the disk?

 

[kwabena]

i cant open disk utility. another way around that?