how to view .sch files
Sorry to say it's not as simple has that you need to know what software created them.
There are plenty that use .sch and .pcb files like eagale layout editor protel dxp and 2004 the new altium 6.5 will open them to but onced saved with altium 6.5 then dxp or 2004 will not open the file.
So you need to find out which software created try eagle layout editor has that is most common software with us hobbyists has they do a freeware version
hope that helps
wizpic