OS upgrade question

You can upgrade to10.7 with Apple support. The process is complex.

Buy a download code from the Apple Online Store for US$20. It is delivered in an email in a few days (the process required human interventions, so it does not happen over weekends or holidays.)

Use the instructions provided in the email to register your code at the Mac App Store. This will cause 10.7 Lion to appear on your "Purchases" page, and you can then download it once or repeatedly from the Mac App Store, using that same Apple-ID.

There is also a hobbyist hack that can add 64-bit support firmware (but running in main store) to the 32-bit firmware already on your early Mac Pro. It is less repugnant than most other hacks of this type because this approach cannot be used to build a Hackintosh using non-Apple Hardware.

Search for 64-on-32 (sfott) to find a blog describing how it works. This is NOT supported by Apple, and if you are a strictly-creative type, I suggest you avoid this approach. WHEN a problem develops, you need to be able to decide whether it is caused by the hack or by something else.

Readers (with the right attitude) report this hack works fairly well.

Link for Lion.

Lion

Check to make sure your applications are compatible. PowerPC applications are no longer supported after 10.6.

Application Compatibility

Applications Compatibility (2)

Do a backup before installing, preferable 2 backups on 2 different drives.