There will be a command in AUTOEXEC.BAT or CONFIG.SYS root directory of C:\ which is calling for a file which can't be found.
checkout these files with a word processor (Like NOTEPAD) and verify that all the files in them exist on your PC.
stop a line of either of the files from executing, by putting a REM statement at the front of the line (eg. REM mode con codepage prepare=((850) C:\WINDOWS\COMMAND\ega.cpi)
note that REM in config.sys produces an error (if i remember correctly), but it stops the command anyway.
another option is to find the boot-up option to "single-step" through the commands in AutoExec and Config, and see which produces the error. I think this is activated by hitting F8 during boot-up, but someone else may advise better