How do I update from OS tiger 10.4.8 to Snow Lepord 10.6?

First question, does your iMac meet the specs for Snow Leopard?

If is does then you will need to purchase the install DVD for Snow Leopard.

Allan

Snow Leopard is 10.6.x, 10.5.x is Leopard.

Leopard requirements/10.5.x...

* Mac computer with an Intel, PowerPC G5, or PowerPC G4 (867MHz or faster) processor

minimum system requirements

* 512MB of memory (I say 1.5GB for PPC at least, 2-3GB minimum for IntelMacs)

* DVD drive for installation

* 9GB of available disk space (I say 30GB at least)

You have to call Apple & likely ask for a Product Specialist to get it, if they still have it! Helps to tell them you have an iPad/iPhone & you can't run 10.6.

There are workarounds if the 867MHz is the only hangup...

http://sourceforge.net/projects/leopardassist/

List of Applications Not Compatible with Leopard...

http://guides.macrumors.com/List:Applications_Not_Compatible_with_Leopard

Snow Leopard/10.6.x Requirements...

General requirements

* Mac computer with an Intel processor

* 1GB of memory (I say 2GB at least)

* 5GB of available disk space (I say 30GB at least)

* DVD drive for installation

* Some features require a compatible Internet service provider; fees may apply.

* Some features require Apple’s MobileMe service; fees and terms apply.

Which apps work with Mac OS X 10.6?...

http://snowleopard.wikidot.com/

It looks like they might still have it...

http://store.apple.com/us/product/MC573Z/A?fnode=MTY1NDAzOA

If it's a core Duo & not a Core2Duo, then it'll only run in 32 bit mode.