What is the best way to link two PCs?

If you have two PCs next to one and other, is there anyway, other than setting up a home or small office network, that the two machines can combine and share processing power?

You can link two pc's in a number of ways. Wireless Networking would be one option, or hard-wired to each other via a cross-over cable could be another, for example.

You can use these methods to share an internet connection and/or share files & printers.

You cannot, however, combine the two to 'double-up' on processing power, it just doesn't work like that.

Hope it helps.

What do you mean by sharing processing power? If you want them to work together to run a processing-intensive program, that's probably difficult or impossible and ways to do it, if they exist, are beyond my knowledge.

If you want to share files and printers between them, then you do need to set up a network (though that can be as simple as connecting them together with an ethernet crossover cable). If you use broadband, you might as well just buy a router as that will share the internet between them easily as well.

Not in a way that is useful for the average user.
Small PCs can be "clustered" using software such as Linux to create virtual machines so that multiple computers appear as one computer to the application.
This is what Google does to create it's data centers.
But the application and the operating system you run must be designed to work in that environment. Plain old Windows and Office or Doom will not work here.

nope.. is the short answer

cpu sharing is really for

rendering farms (to do cgi graphics)

cpu heavy tasks.. e.g. music studios. .my friend has 2 extra pc's that run instruments, to share the processing load as the instruments take a lot of CPU power.