How you can have images larger than 500 MB in official DOSBox:

- Create one with BxImage.
The geometry values have to be recalculated:

Cylinders maxes out at 1024 for DOSBox, however heads can be up to 256.
BxImage will suggest a cylinders value above 1024, so divide cylinders by 2 and multiply heads with 2. Cylinders still bigger than 1024? Do it again and again. You'll get up to about 8 gigs with that.

Example:

From BxImage: -size 512,63,16,1422
Recalculated: -size 512,63,32,711

Take a look at these threads:
Maximum HardDisk size emulation.

Problem with the Harddisc Image Totorial

Regards

I just noticied today that if you do not specify "-size" and use the autodetect feature then you will be unable to create a partition using FDISK.