dai is right. There are a lot of things working against you here.
RAID formats are proprietary, so different manufacturers are not automatically compatible. With RAID1 the situation is usually easier, as each drive is pretty much a normal image, but with RAID0 there are no guarantees. But with RAID0 the tradeoff is performance vs. recoverability & portability.
Because of the propietary factor, the only tiny chance of success comes if the chip on the MSI which created the array, was the exact same chip as on your new mobo, i.e. Intel 875P or Promise PDC20378 in this case, depending on which chip you used. That might get you part of the way there, assuming you could get the Asus chip to recognize the array without trashing it-- which with RAID0 is questionable. A 875P-Neo-FIS2R is an example of an MSI board that used the same i875P and PDC20378 chips as P4C800-E, but I don't know what MSI mobo you were coming from.
If you could get the array to be recognized, the repair dai mentioned would be the next required step. A "Repair install" is practically a full install and takes almost as long, except that the partition+format steps are skipped and some (data) files are probably preserved. This install would be necessary because the old installation, when it tries to boot, won't find all the exact same internal mobo devices at their same hardware addresses where they were on the old mobo. So it will give up and retry, again and again, and never finish booting. A repair install fixes this by replacing the old onboard-device drivers with new ones compatible with your new mobo. Once Windows finally boots, other new-mobo drivers must then be added, starting with the chipset utility. In the case of RAID, the appropriate RAID driver probably also has to be loaded at F6 to facilitate the Repair by making the array chip visible to the Windows CD.
If there is any chance of putting the drives back into the MSI then burning the data files to some sort of backup DVD, that would be your best bet of moving your data. I would make a couple copies just to be safe.
Hope this helps,
-clintfan
