system.ini belongs to windows (3.x/9x/...)

What program does not run under dosbox, yours
or clipper itself? Are you sure both are dos progs?

There are explanations on how to run clipper
under XP, like http://www.tek-tips.com/viewthread.cfm?qid=942760&page=1

wd

I'll specify where this option are set under DOS but it seems to me that it's in config.sys. Anyway I've found in this program only commands section but not DOS configuration. Also I'm not sure what is wrong because I can't read a message in a cyrillic font. It was running OK some time ago but one moment it became not starting and the only solution I've found is using DOSBox.

A problem with cyrillic fonts I've soluted and found that when programs starts occurs error 2 of opening file.

error 2 hmm file not found ? i think or path not found but i would go the former.

I've thought may be a line
Path=e:\Ilya\DEK_OSN;e:\Ilya\DEK_OSN\SOURGE
doesn't take effect but I don't know why.

set path=... maybe ?

Official MS-DOS allowed variables to be set without writing "SET", allowing for lazy stupid programming 😒

I've solved this problem and it was that it started from Z: disk instead of E: so adding changing directory to E: has helped. But I've met another problem - the program runs to slowly and I can't find anything in configuration to make it run with a speed near to that it'll be executed using direct starting. What means cycleup I've not understood and others in CPU section don't affect.

Ilya, look at section 5 (Special Keys) in the ReadMe for a short explanation of increasing the speed of DOSBox using the CTRL+F12 key.

Also - have a look at the Running Resource Demanding Games page on the DOSBox Wiki.