will this computer run X3?

Is this enough processor for X3?  I am installing Windows 7 64 bit on it.

You may find running Windows 64 bit and Sonar, with only 4GB of RAM, that your track and plug in count may be limited. This of course depends on exactly which plug ins you are running as some will require more RAM than others. Others here will be able to tell you which plugins and synths are the most RAM hungry. But Sonar X3d will run, just experiment and you will discover what works and what doesn't.
If you can give the computer a RAM upgrade you may find this will help more than anything else. Don't forget to tweak Windows, as this will help with XP.

rebel007
You may find running Windows 64 bit and Sonar, with only 4GB of RAM, that your track and plug in count may be limited. This of course depends on exactly which plug ins you are running as some will require more RAM than others. Others here will be able to tell you which plugins and synths are the most RAM hungry. But Sonar X3d will run, just experiment and you will discover what works and what doesn't.
If you can give the computer a RAM upgrade you may find this will help more than anything else. Don't forget to tweak Windows, as this will help with XP.

I've only 2gigs of RAM and got a profect running 64 audio tracks. A couple of "Audio Dropouts," but that seems to be due to HDD usage.

mixmkr
How can he use WinXP sp3 and run an unsupported X3?  Also with XP, how can he use more than 2 gigs of RAM?  XP "pro" can utilize more than 2 gig, I guess?

He's going to install Win7 on it.

I had an ASUS P5B that, if I remember, will only run DDR2, and requires matched chips to wring the max of 8 GB out of it without memory problems.  I changed mine out for a motherboard that had socket 775 CPU support (so I didn't have to buy a new CPU) and supported DDR3, which is much faster (and probably cheaper) than DDR2.  Mobos with socket 775 and DDR3 support may be getting hard to find nowadays, but there should still be some out there.  This would at least give you some capability for upgrading to a more powerful CPU or more memory down the road without breaking the bank.  Otherwise, you will be able to run Sonar X3 with what you have but you will probably encounter some memory limitations at some point.