Upgrading OS 10.5 to 10.6 -Can I use my laptop OS CD on my desktop to upgrade?

Upgrading OS 10.5 to 10.6 -Can I use my laptop OS CD on my desktop to upgrade?
thanks

If you are talking about an OSX DVD that came with your Mac Laptop, then no. The DVD's that come with any Mac are for that exact machine of those specs only and will not work on a different Mac model.

If it were a full retail version of 10.6 then yes, but legally unless it's a Family Pack license it can only be used on one system at a time.

With 10.7 Lion though one copy from App Store can be installed on as many Macs as you own and are registered with Apple!

Can i just directly upgrade from leopard to lion?
The only reason to go to snow leopard was I was told I needed to upgrade to that before Lion could be installed-
Also- I've read some pretty disturbing things about the stability of 10.6 snow leopard- any experiences?

I do not know where you are reading all these issues about Snow Leopard. Snow Leopard is in fact a VERY stable OS. One of the best Apple has ever made in my opinion.

As far as an upgrade to Lion, you will have to have Snow Leopard first. If you were doing a clean install of Lion, you could get the USB stick and just install but that costs something like $60.

Go with the USB stick for Lion at $69. The route via Snow Leopard will cost 2 x $29 and for the $10 you will have Lion on a bootable USB thumb stick. Do a clean install by formatting the drive, after popping your existing internal into an external case and keeping as a backup in the event you do not have a current backed up external drive.

Update to Lion OS X.7.3 using the Combo Updater and then use Migration Assistant to transfer everything across from your external drive.