Change the boot drive from A to D

Hi All

Well I thought I would be clever and put a new c drive in my PC All fine until trying to reboot from my XP disc. It refuses to do anything no whirly sounds or anything. I have done it before and it worked fine so a bit stumped. Anyway I made a floppy boot disc and have got the A prompt up. I suppose I have to give it a command to open the CD Drive ( E ) but I've tried all the ones I know and just keep getting bad command etc. Any ideas on the command or how to reboot any other way ?

 

Sorted. I took a leaf out of Stringbeans book and took the power out of the floppy and hard drive so it had to use the CD once it had booted up I put the power cables back in and Hey Presto!