ok, some news: using fdisk /mbr works and make the CF bootable, tanks to all. But i have one new problem... using 512Mb Sandisk CF seems to work properly but during the DOS 6.22 installation, it say me that the computer have some problem to write some file, like qbasic.exe and so on... using instead a 128Mb cf Sandisk DOS install without problem.. my question is: Even if the BIOS seen the 512MB sandisk the computer not use it correctly?

AlessandroB wrote on 2023-06-21, 19:27:

ok, some news: using fdisk /mbr works and make the CF bootable, tanks to all. But i have one new problem... using 512Mb Sandisk CF seems to work properly but during the DOS 6.22 installation, it say me that the computer have some problem to write some file, like qbasic.exe and so on... using instead a 128Mb cf Sandisk DOS install without problem.. my question is: Even if the BIOS seen the 512MB sandisk the computer not use it correctly?

Nobody ever replied to you here, but yeah, you might have a 504 MB BIOS limitation. Read my previous comment on that. Try to make the partition on the 512 MB CF smaller, like 450 MB, and see if you still have the issue. If yes, you may have to use smaller cards unless you use XT-IDE BIOS or something like that.