Windows 7: Setup raid 0 after install

Can you setup a riad 0 after win 7 is installed, I have 2 1tb drives, win 7 on one other not setup yet.

Yes, go to Disk Management and set up a new mirrored volume. I am not sure: you may need to convert to dynamic disk for it to work.

What are the pros and cons of doing it this way, or should I do a fresh install and enable the raid and set the array to 0 then install.

N/A. Doesn't matter which order you do it in.
Edit: after posting, I realized that the only difference it will make is that after you have put stuff on the drive, it will take longer to sync than if it was empty. This is a one-time thing, however, and the time you spend doing a clean install exceeds the initial sync time.

What I meant was should I try to stripe it in windows, or do a fresh install and setup raid then install win 7. Never used raid before, I have read and understand it now.

If you motherboard supports it, I would recommend using RAID at that level. If not, or you want to do it the easy way, so it in Windows. I have never used RAID, either, just played around with it briefly.

If I do it windows, will I still get the Raid 0 performance.

It will use your CPU instead of whatever resources the board uses. In short, probably, but it will use slightly more resources. In all honesty, you will probably not notice a difference.

Has anyone compared a raid 0 setup in Win 7, verse a raid 0 done during install.

The "only" reason that I would use a RAID 0 implementation from within Windows was if my mobo didn't support RAID and I absolutely needed the extra drive space and simply could not afford another standalone hard drive with enough capacity. You won't really get the performance benefit of RAID 0 from Windows striping that you would get with a real RAID card.