Booting up Windows 98

When booting up Windows 98 the Manufacturers logo flashes on the screen followed by a black screen followed by the Windows 98 screen then a black screen. Everything seems O.K. until now. The next screen is a dos c: prompt. You can use dos but cannot bring up W98. It does same thing in Saft Mode. Disk has 1,156.80 MB free space. Can delete file from disk but free space does not seem to get larger.