Bootmgr missing

[Schnyd]

My computer locked up today and I had to restart it. Upon restart I got the error BOOTMGR is missing.  I tried to repair using the windows disk but it states that it is unable to repair. What are my options?  

Computer Specs:

Windows Vista 64
4 gigs ram
Raid 0 using on board controller (2 x 250 gig hdd)
Asus M2r32-MVP motherboard

Any help I can get would be greatly appreciated..

Thanks

[Schnyd]

Well I got it sorted out some how. Along with my raid set up I have a IDE hard drive thats used as a backup. I partially installed vista on that drive and then upon restart it gave me the option to but into my new install or my 'Windows Vista (recovered). I chose 'Windows Vista (recovered) and it put me right back into my computer as it was before.

I'm wondering what causes a Bootmgr to fail. This is actually the 2nd time in 30 days I've had this issue. As well whats the best way to protect against it?

THanks