Hi Jan,
Thanks for your post. You can find generic computer equipment in the Library List under Generic Audio | Electronics | Computers
All symbols are editable so you can create manufacturer-specific symbols from the generic ones we supply and save them simply by dragging them into the Library List under My Libraries.
In a Block Schematic you you can use a wizard to create new symbols you need (Tools | Symbol Wizard)
I hope this is helpful
Regards
Rob