Can't type Alt codes Help!

Hello,

My brother has a dell laptop:

Dell Inspiron n3040

HDD 320 GB

Processor i5

512 VGA

When he tries to type an alt code, Windows can't do it.

For example: Alt + 0158 (ž)

When he presses Alt and then presses the numbers keys at the top of the keyboard, he hears sound coming from Windows and just doesn't type in the alt code.

Is there an alternative way for that?

Thanks