Windows XP boot failure

[Glenn]

I've had XP sp-1 running for several months.
Yesterday, while booting up, I got the message, invalid
boot disk, insert valid disk and press enter.

I insert my WinXP cd and after a few seconds, it boots up.

If I leave the Win XP cd in the cd player, next time I
start the computer, it starts normally. But, only if the
cd is in.

What's going on?

 

[Rich Barry]

Glenn, make sure you don't have a disk in the Floppy Drive.

 

[The Unknown P]

It sounds like either you MBR(master boot record) or your
personal boot record has become corrupt. Once you have
gotten to your desktop then go>start\run and type in
msconfig and then click the boot.ini tab and then the
check all boot paths button. If it finds a bad boot path
it may ask you if you would like to write a new one.
Choose yes and follow the on screen prompts. Have fun.