Just a guess on my part but it should run just fine. Is CS4 is a 32 bit program? If so will Win8 let you run in 32 bit mode? Adobe will not give you an answer as version is outdated and no longer supported.
If you are really interested in upgrading you have until Dec. 31 for the upgrade price, then it is full price.
Did you find out yourself if your Adobe CS4 applications will run in Windows 8 Pro?
I have an existing Windows 7 x64 laptop that I am considering upgrding to Windows 8 Pro, but as it contains my mobile install of CS4 Web Premium and InDesign CS 5.5, I am cautious about making a radical change that would result in all of it being rendered useless.
At least the version of Lightroom (4.2) was listed as compatible...
I concur, all CS4 apps (32-bit* - see below) run quite well in Windows 8 Pro (64-bit). I am experiencing better performance than when I had XP Pro 64-bit on the same machine; However, the following may be of interest:
1. CS4 was never certified for 64-bit systems and the latest service pack was a prerequisite for all previous 64-bit Microsoft operating systems.
Sidenote: The latest service pack for XP 64-bit is actually found under the Server 2003 Service Pack downloads on the Microsoft site.
2. All CS4 products are actually only 32-bit except Photoshop which exist in both 32 and 64-bit versions in the installer.
Regarding Photoshop (in my experience - see my system details below for comparison):
1. The installer is supposed to install the 32-bit version on 32-bit systems and install both the 32 and 64-bit versions on 64-bit systems, however, with Windows 8 Pro 64-bit, it only installed the 32-bit version of Photoshop. (I then wiped my drive, reinstalled the OS and then reinstalled CS4 chosing the 64-bit version of Photoshop in the custom install options)
2. If you manually select to install the 64-bit version of Photoshop (in lieu of the 32-bit version using the custom install options), the 64-bit version will fail to run, even using any of the compatibility options provided. (I then wiped my drive and went back to a default install of CS4).
Be aware that if you select to install Photoshop (64), it may not run and since the 32-bit version is not installed when the 64-bit version is selected, you will have to uninstall the 64-bit version and then reinstall the Photoshop component allow the default 32-bit version to be used.
Machine: Toshiba R25-3513 convertible TabletPC
Processor: Intel Core2 Duo processor (T5200) (Does not support hyperthreading - which may be my issue)
OS: Windows 8 Professional 64-bit