Have to upgrade to Mountain Lion. Want to wipe my drive, but can I then restore apps and data from LEOPARD backup on Time Machine? So my lovely system that has been working wonderfully is finally out of date, as enough developers are no longer supporting it. I have to upgrade to Mountain Lion on my intel macbook. 

I'd like to take the opportunity to clean the drive and start pristine, but I don't want to have to go through the process of reinstalling a damn large amount of applications from their install disks. I also don't want to lose all my data. 

Is it possible to do a clean install of Mountain Lion, and then restore applications/preferences/data from my last backup of my 10.5.8 system? 

Is there a better way to accomplish what I'd like to do? 

Thanks.
It is possible to do a clean install and then restore your applications and data if:


Your MacBook supports Mountain Lion (check this http://support.apple.com/kb/HT5444)
You can somehow manage to buy the OS X installer on the Mac App Store (Mac OS X Leopard can't access the Mac App Store, you need at least Mac OS X 10.6.6).


Once you have downloaded the OS X installer create a bootable USB drive or DVD (for example, see here).

Note that Apple doesn't support updating from 10.5.8 (Leopard) to 10.8 (Mountain Lion) (http://www.apple.com/support/osx/getstarted/):


  If you’re running OS X Leopard and would like to upgrade to OS X
  Mountain Lion, first you’ll need to upgrade to OS X Snow Leopard. You
  can purchase OS X Snow Leopard for $19.99 online via the 
  Apple Online Store.


so the Migration Assistant may have some trouble restoring your applications and data from your Time Machine backup, or even reject doing it. In that case will have to copy your applications and data manually.

If anything goes wrong you can restore Leopard from your Time Machine backup booting from the Leopard DVD (I did that once with my old PowerBook and worked like a charm). If you don't have the media, I'd recommend that you create an image of your current harddisk (for example, see this or this).