It's interesting how much of a difference there is between Windows 8 and XP when it comes to running Photoshop.

Source: Operating System SmackDown: Windows 8 blitzes XP on 7 year old hardware ę Troy Hunt

I know thereís this unwritten law that newer software requires more resources but my experience with Windows 8 has always been thatís itís way faster certainly than Windows 7 was on the same hardware, but itís my recollection that XP was never really as snappy as 8 is now on any hardware. So I dug up the oldest, crustiest hardware I could get my hands on and did some tests

If you just want to skip straight to the results, hereís the rundown:

Lenovo T60 (released in 2006)
1.83 GHz Intel Core Duo T2400 CPU
7,200 RPM mechanical drive

And the results:

... both operating systems were installed via DVD, they were 32 bit and both were patched with 100% of critical or important items from Windows Update. They were also both running Microsoft Security Essentials and the other software seen in the demo (Office 2013 in Win 8 and Office 2003 in XP, Adobe Reader and Photoshop CS3). The boot test was done by shutting down from each OS then powering on.