How can I get an install of 10.7.5 for my MacPro 1,1

About OS X Recovery - http://support.apple.com/kb/HT4718.

No, you just need to boot into Recovery mode.

- restart holding down the option key

- on the resulting window, select “Recovery HD”

- you will be asked to choose a language

- this will boot to the “Mac OS X Utilities” screen

Are you sure you are currently running 10.7 OS? Both 10.7 and 10.8 have this recovery mode option, however previous versions of the OS don't.

option key and the option+r

That needs to be Command-R.

It needs to be held down immediately at Startup. (not in an already-running system)

And it needs to be on a keyboard Directly connected to a USB on the chassis, not through a display or any other Hub.

I have a MacPro 1,1 which was working just beautifully until a few days ago when my email was hacked and I am certain that something is going on with the machine. It crawls with operations it used to breeze through. I've installed virus protection software and it says nothing is wrong, but I just want a clean install. I know something is wrong.

Whatever is going on isn't malware. E-mail accounts get hacked all the time, and it doesn't require anything from your computer to do that. The timing is undoubtedly purely coincidence, especially if you have done a scan with decent anti-virus software. Which software did you install?

Regarding fixes, you may find something that will help without requiring a clean reinstall in my Mac Performance Guide.

If nothing there helps and you want to do a clean reinstall, as Grant points out, you've got to use a properly-connected keyboard. Grant didn't mention Bluetooth keyboards, but note that I've heard mixed reviews on how they work for this purpose as well.

If you are using a directly-connected keyboard as specified by Grant and holding down the option key by itself, starting as soon as you hear the startup chime, does not result in some kind of recovery disk showing up as an option to boot from, then something is wrong with your recovery partition. In that case, what you'll need to do is erase the hard drive and reinstall Snow Leopard, while booted from a Snow Leopard disk, then update to 10.6.8 to get the App Store, then re-download Lion and install that.

Good points, Thomas.

One other issue users encounter with holding the Option key alone...

... this routine is all in ROM. Nothing is needed from ANY drive to draw the initial screen.

But the entire procedure seems like it unfolds in slow motion. It takes several minutes to show all the Icons for all the potentially-bootable Volumes.

You must be very patient.