Please Help Me ASAP,I Need Big Help For My Toshiba Tecra 730CDT?

I Have A Toshiba Tecra 730CDT That I Bought From EBay And I Recently Reformat It To Clean Up My PC Using MS-DOS.I Was Running Windows 98 Then But After Reformat,My Laptop Show An Error After Startup Saying"Invalid System Disk Please Replace Disk And Press Any Key."But I Have No Boot Disk Or Windows 98 CD When I Bought The Laptop,Not Even The Recovery Disc Was In There,I Tried Creating A Boot Disk Of Windows 98 From The Internet but It Did Not Work And Still Showed The Error,Please Help Me As This Laptop Is Important To Me.If You Need Any More Details,Please Do Not Hesitate To Post The Questions And I Will Reply ASAP.