Still no budget then eh?
The reason CS4 keeps crashing using Win 7 64 Bit is probably because of dated hardware.
It runs fine for me on a four year old machine using Win 7 64 Bit, as does all other software and latest games.
Ok, let's assume you keep the case, hard drives and optical drives.
This means you need:
Motherboard with integrated graphics
Memory
CPU with stock cooler
Power supply (very important)
Possibly a new widescreen monitor.
Again, I politely request available budget.
And also monitor size.
By the way, if you change motherboard etc your old Windows installation is extremely unlikely to run on it due to different motherboard drivers so you will have to do a fresh installation of Win 7. The key word here is backup.
And less of the age thing please, I am less than two years younger than you and hopefully I don't have one foot in the grave yet