PS CS4 hangs, stalls, freezes either during start up or immediately after causing the computer to become unresponsive.

System

* Dell XPS720,
* 24" Dell WFP
* XP MCE,
* 4 gig ram, (2.75 available)
* 250 gig free space on 750 gig Hard Drive,
* NVidia GeForce 8800 GT & newest driver,
* Canon MX700 & newest driver.

Here's what I've done so far, (sorry if I missed any thing)

* No recent updates or changes to system until after issues started.
* Renamed PREF's file - no change. (new pref's file has 0 bytes)
* Tested system components - all passed.
* Uninstalled, restarted, reinstalled, restarted software - Result = No change.
* Updated drivers for printer/scanner & video card - Result = No change.