Critical: How to fix MBR on Ubuntu/Vista dual-boot laptop?

Is your ntldr actually MIA? It's just a file in C:\, though it's hidden so your explorer has to be set to show all files in order for you to see it. Or you can check in a command window. (This is XP SP3): C:\>attrib -s -h ntldr C:\>dir ntldr 06/09/2008 08:30 PM 250,048 ntldr 1 File(s) 250,048 bytes If it's actually gone, you can just copy it over from another system with the same OS (and maybe the same service pack level also, just to be safe.) If you really have a problem with your master boot record you can write a clean new one with fixmbr, but that will cost you your Ubuntu install.

The NTLDR not found message seems to mean that the disk is not readable to windows--like that there is an MBR problem. It's not that the file has gone missing; it's just the first thing found missing.

http://www.supergrubdisk.org/ is a lifesaver when it comes to MBR problems. Simple and tiny download, burn to a disk or what have you, boot off it, and it'll give you nice menu where you can fix just about any MBR problem.