Although the Missing NTLDR error is quite upsetting and appears to be quite fatal, it is actually one of the easier problems to fix. Before it happens to you again, see (and save) the following MS Knowledgebase article.
If you have a floppy disk, you can format it as a bootable disk and copy to it two files:
Then, if you have the problem, boot from the floppy and copy the two files back to the C:\ drive. When it happens, you will probably find that all files in the root of C: have been lost. What I also did, in addtion to making the floppy, was to create a directory into which I copied all the files in the root of C: so I could get them all back.
This doesn't prevent the problem from happening, but makes it easy to recover.