Agreed. 533Mhz wont even power Windows 7 let alone any programs. I had a 333Mhz about 8 years ago, and even then it was a really old Dino. I have a Dual Core 3.4Ghz now and its outdated (Pentium D 945). And another thing, even if you find the upgrade and are willing to pay the premium, its not a big upgrade. Prolly not even noticable.
You can build a computer for about 300-400 if you skimp out