Critical error during PS CS4 installation

Question

I have just purchased the download version of Photoshop CS4, but unfortunately it won't install...
After having unpacked to the default location (desktop) and starting setup.exe, the "Adobe Photoshop CS4 Installer: Initializing" dialog appears. When it's just about 90% finished, the "Adobe Photoshop CS4 Install-Loading Setup" screen appears along with the message "Critical errors were found in setup Please see the Setup log file for details" This window is titled "Windows Internet Explorer"
It does not say where to find the log file or what its exact filename is.
Windows XP SP3 English version, Intel Core Duo 6600, 2Gb RAM, Ati Radeon X1950XTX.
I've had trials of Photoshop CS3 and Lightroom 2.1 on this system in the past. These have been uninstalled. I've also ran the
CS3Clean.exe script.
I also had Photoshop Elements 3 which I've also uninstalled.
Any suggestions welcome!
Martijn

Answer 1

Hi David,
[With apologies for straying off-topic]
Im unaware of any programs or tools installed with Windows that will restore an identical copy of your registry. Besides ERUNT, several of the fix-it or registry cleaning/tweaking programs can back up & restore your entire registry, including the popular CCCleaner, but Ive seen so many folks get into trouble *Cleaning* their registry, I dont feel good recommending any of them. Of course you shouldnt have to use any Cleaning features to backup & restore your Registry, but the temptation is always there. ERUNT on-the-other-hand is a One-trick Pony, & does nothing but backup & (if need be) restore your registry, & for pre-Vista Windows I cant recommend it enough.
Typing Regedit into the Run box starts the Windows program of the same name, and it works fine exporting backups of individual keys, sub-keys, or even the entire registry, BUT, while merging back individual keys, or importing saved, partial registry backups works fine, you cant restore the entire registry with Windows running... you cant replace any keys/values that Windows is using at the time, so you have to restore the registry outside of Windows.
This is something many sites get wrong, & Ive seen recently where Adobe has repeated this mis-statement too, advising their users to backup their complete Registry using Regedit. A relatively harmless way to prove the point is to set a Restore Point [out of an abundance of caution ;^) ], backup your entire registry with Regedit, then try to merge the exported .reg file. IMHO its better to find out it doesnt work *before* you really, REALLY, need it to work.
Backing up & restoring the entire registry is what Windows System Restore is supposed to do, since it changes things during a reboot/restart, before Windows fires up. The problem with System Restore is that it wont always delete every new key or value added, just like it wont delete every file change since the Restore Point was created. Vistas System Restore is better than earlier versions of Windows, keeping a shadow copy of your drives contents in a special format, but its not perfect. [note: just looking at that drive in other operating systems will delete any restore data if they dont understand the special format Shadow Copy uses]
If a person is experienced with Registry editing, in this case IMHO theres nothing at all wrong with using Regedit to export (save) just the Post Platform keys with sub-keys they plan on deleting. But if someones unsure about Registry editing, or just wants an extra measure of safety, back up the whole thing first using whatever favorite tools - just make sure restoring your backup works, or youve wasted your time.
Thanks,
mike