Some programs are easy to convert: you can simply (b)load them and save them on a disk. You can use the header info to know the proper addresses. However, some programs are so big, they would use the memory area which is in use by the disk BIOS. Such programs can only be converted by breaking them in 2 and loading them on the lower 32k pages. After loading, kill the disk BIOS, and move the program back to the higher memory region where the disk area usually is. Then execute. There exist s a few utils that can do this (e.g. in Dutch magazines like MSX Gids they were published (e.g.: Bytebreker)), but the success rate will still be pretty low. Best results are usually done by experts who have to put in some dedicated work to convert the program to disk.
There is no fixed rule to convert a program from tape to disk.
If you can load (or cload or bload) from tape, then it is (almost) sure that you are able to save it bac to disk but, as manuel says, if the program is too big to fit in the available RAM then you will have to make special loader (just study their loaders...).
Another problem is that if the program you are loading is not saved i a standar format (i.e. spectrum-like, no header, etc), then you will need to use a special loader ...
Once you have converted a couple, then you can figure out how to convert a lot but, as i said, there is no fixed rule or program to do it.
