Firstly, what does it say when you try?
When you start the computer i assume you know to hold down Ctrl. That should get you to the Safe Mode thing, chose command prompt only, easy... But i am gonna assume you already knew that, if not well then.. *coughnewbiecough* haha... nah anyway if that fails... tell me the messages it comes up with off the top of your head... Or try using a windows 98 boot disk to get to DOS.
If all else fails try formatting and starting again because sometimes something gets corrupted that has to do with DOS and it won't let you use it...
Anyway, get back to me`
AMD Tbird 1.1Ghz & SuperORB
Asus A7V
128MB PC133 SDRAM
Winfast GeForce2 MX
Win98 SE