The more I research the problem the more it seems likely that it is caused by the MFT (Master File Table) on your hard drive becoming too big and too fragmented. This is caused by a number of factors, but you are most likely to have this problem if you have used more than 87.5% of the available space on your primary hard drive (at any time in the past). The more files you add and delete, the more fragmented your MFT will become. Adding a large number of files (for instance, installing a large program like EMC 10) could trigger the "NTLDR is missing" problem.
See also... http://www.diskeeper.com/eletter/previous/...1999110261.html
If possible, I would like to ask you and anyone else affected by the problem to do the following...
1 - Check your MFT fragmentation. Open My Computer. Right-click on your boot drive and choose "properties". Choose the "Tools" tab. Choose "Defragment Now...". Select your boot drive and press "Analyze". Choose "View Report", and under "volume information" scroll down to the section that describes your MFT. Please write these values down and let us know what you find. If your MFT is in more than 2 fragments, or if more than 90% of your MFT is in use this might be the cause of your problems.
2 - Clear off as many files from your hard drive as possible. Back them up to CD, DVD, another hard drive, or simply delete files that you no longer need. Ideally you should have at least 30% of your hard drive free.
3 - use an advanced defragmentation tool that offers "offline" defragmentation of the MFT (this would happen when you reboot, before Windows starts). I would start with Diskeeper 2007 (they have a free trial available).
4 - Re-check your MFT size and fragmentation (repeat step 1).
5 - Install EMC 10.
I look forward to your (hopefully positive) feedback.