Word for a laptop or desktop, but not a smartphone or tablet

I would suggest computer (in agreement with Dan Bron's comment).

You're not trying to win a medal for ontology, you're trying to point people in the right direction. Laptops and Desktops are commonly called computers, those other devices are not.

This would be strengthened by adding a contrasting reference to something like mobile device, mobile, or phone nearby. (For example saying how such things are not available from mobile devices or are available elsewhere).

I think using these terminologies would minimise genuine confusion at the slight expense of annoying pedants who could think of counterexamples (You are actually assisting these people as well, in satisfying their need to find examples with which to demonstrate their linguistic superiority to others).

You're question is unclear, but you probably mean Desktop

The ubiquitous formulation is "this dotcom works on both Desktop or Mobile!" or "We have apps for Desktop and Mobile!"

Another formulation (if for some reason you don't want to say what everyone else does, "desktop or mobile") is just "For Mac/Windows, or, Mobile". So you can use "Mac/Windows".

Just regarding "desktop". Not unreasonably, DB has pointed out that, say, 295 years ago, people referred separately to "Lap-Tops" :)

Don't forget - if I tell you "this [whatever] is for a desktop", then of course, obviously, that same software or hardware also runs on a "Lap-Top".

So again, it's totally normal to say "Desktop or Mobile" and this would be why you can find a million goole hits for that, including, it's the language google's ad agency uses

And finally here's a link to the all time classic

SHROVIS-BISHOPTHORPE Envaliant III

sequence, since you may have misplaced yours.

http://achewood.com/index.php?date=04012008

Your best bet is "computer" or "PC". Laptops and desktops are understood to be computers or PCs. People don't usually think of smart-phones and tablets as "computers".

+1 @DanBron

Of course, you and I know that all mobile devices contain computers (CPUs), but then so do microwave ovens, TVs and cars.

One way could be to call it a real computer. Example usage in this comment by tchrist. If you google search for real computer, you will find more usages of this meaning. In particular when in contrast with tablets or smartphones, chances are people will understand what you mean.