I found this reference to BootMagic on PowerQuest's web site:
Solution: Error finding BTMagic.img
If there is no disk compression, no Direct Drive Overlay (DDO), and no virus in the master boot record on your hard drive, perform the following:
1. Boot up with a Windows 98 boot diskette.
2. Make sure that you have a current backup of the data on your drive, and then run FDISK /MBR at the A:\ prompt.
NOTE: For more information on FDISK /MBR, please see PowerQuest Solution PR171, "What does FDISK /MBR do?"
3. Press Enter.
This removes the flag from the master boot record.
If the preceding solution does not solve the issue, perform the following:
1. Boot up with the BootMagic Rescue diskette.
2. At the A:\ prompt, type: wrprog /rst mbr.dat
3. Press Enter.
The master boot record will then be returned to the way it was before BootMagic was installed.
Here is the URL to this page:
http://www.powerquest.com/support/primus/id40.html
(please remove any spaces)
Hope this helps.