To free up space in DOS... Copy stuff you want to some convenient storage media (CDRW drive, tape drive, floppy...) before deleting it. Put the line set dircmd=/a /p in AUTOEXEC.BAT so your dir command shows all files and displays them a page at a time, and use ATTRIB command to clear Readonly, System, and Hidden bits from superfluous files (like in the %temp% directory) before deleting them. Check the %temp% directory (should be c:\temp or c:\windows\temp, but some setups actually use the c:\dos directory...) and delete all TMP files. Empty any 'delete catcher' or 'recycle bin' directories.
Downloading Win95? If you're trying to get a pirate copy of an OS, give it up and get Linux...