|Windows 7 is not ready for prime time yet and besides you should never install TWO operating systems on one partition/array. |
Which OS are programs installed to?
You may be able to recover some personal data by using recovery programs or a live version of Linux, like Knoppix.
As far as the 500GB drive goes Microsoft states that defrag will not even start with less than 15% free space. You should not have placed too much data on there.
Maybe your easiest solution is to install WinXP to the 250GB and then use Winxp to access the RAID array to recover personal data. Then worry about fixing the RAID 0 array.
As jam mentioned not many of us here are booster of RAID 0. More trouble than it is worth. Maybe you should think about using the disks separately with OS on one and programs on the other.
I don't suppose you maintain any images/backups?
You know there is an addage that goes to say "it is not if your hard drive/s fail but when. Also need to worry about OS going South or catching a nasty. All those issues can be countered with backups.