i was working on orcad 10
but i found that there is some parts like atmega8538 and others not found
i want libraries to download them from the net and add them to my libraries
can any body help?
I had the same problem with PICs, and I couldn't find a site to download the libraries. I ended up making my own libraries, but I have also started a Yahoo group dedicated to sharing the OrCAD libraries https://groups.yahoo.com/group/orcadexchange/ . You're welcome to join. The libraries are in the "files" section. May be the library you're looking for is there. If it's not, you can post a request - may be somebody has it.
The power pins are probably there, they're just invisible. Right-click on your component and select Properties... from the menu. In the properties there should be a field Power pins visible. If you check it, Vcc and GND pins will become visible.