XTIDE - boot menu callback via int 18h

Thanks all for getting me going. I cheated at first with a real Maxtor 20 GB hard drive, and Alexadre's suggestion to FDISK with just a few cylinders, and that worked. Now, going to a CF card, same plan, no errors with FDISK, FORMAT C:/s, and I can see command.com is there if I boot from a floppy. I am able to read/write to the CF just fine, copy to it with /V and all OK. It will not boot from XTIDE, and I get this error. I read that some CF will not work. Can you recommend ones that do, and I will go get one. They one giving me trouble is: Sandisk Ultra II, I have had it for years in the junkbox. SDCFH-2048 is what XTIDE reports. Will a new, current CF fix the problem? Enlighten me on what boot menu callback means. Thanks, Randy