need help on start up

when i start computer mess. comes up [invalid system disk replace the disk] have to go to f12 and type in the c for disk how can i fix this? what have i done to cause this problem? very new at computers!!!help

 

Sounds like you have a floppy in the A: drive, eject floppy?
Bug

 

Either a floppy is in the drive (as posted above), a CD is in the CD drive and for some reason the PC won't 'see' past it, or your boot order in the BIOS is set to where drive C: isn't listed, or is listed last. Enter the BIOS by pressing Del or F1 or F2 (all PC's have different keys for entering BIOS setup) right when you first power up the PC. Then navigate thru the menus until you see something like Boot Order or Boot Device Priority and set drive C: as the first device. It probably won't say 'drive C'. It'll say something like "PM-WDC1234567" where the WDC1234567 is the model number of the hard drive installed; it might say "HDD 0" or maybe "IDE-0"... in any case, make sure it's first, be sure to save your changes, exit BIOS and let the PC reboot, and all should be well.

hd2k