Excel and office compatibility pack

Hi,

my system is windows XP pro and office xp with all updates.
In Administrator I installed the compatibility pack and when I click in a
xlsx file, a small window appears saying that the conversion is working.
Excel opens the file with a strange name and read only.

Can't open it directly from excel, invalid filte type.

When I change to another user account, nothing works, can't open the file in
any way.

Don't know if it works in word or powerpoint since I don't have a file to
test.

Any sugestions?

Best regards
Vitor