Disk Boot Failure, insert system disk(power button)

[movingtables]

When i switch the computer on via the power button on the front of the pc case i get the following message:

" Disk Boot Failure, insert system disc "

all cables are snug and secure however:

"If" I switch the pc on via the case power button but ever so gently the pc boots up perfect every time, but if i press the power button on at normal human every day strengh i get the error message.

so umm what do you think this could be?

 

[movingtables]

anyone ?

 

[movingtables]

after further testing the power button pressing didnt work.
however i did read somewhere that re-installing video drivers could work and it "appears" to have so far but so who knows.
the only things i have done differently in the last week are install a new screen on my pc and i remember only "half" defragging my hard drive and quitting because i had to much stuff to do on the pc lol.

if i choose repair from the xp disc will this repair any corrup boot files if there are any ?