Slow computer start up - any advice?

I have tried de-fragging, anti-virus checks, antispy ware and anti-ad. I even tried downloading 'ccleaner' after reading advice given to someone with similar problems. My start up is particularly slow and alsways comes up with a black screen saying "initalising error. Re-booting from windows... show more I have tried de-fragging, anti-virus checks, antispy ware and anti-ad. I even tried downloading 'ccleaner' after reading advice given to someone with similar problems.
My start up is particularly slow and alsways comes up with a black screen saying "initalising error. Re-booting from windows (:/c)" or something similar (don't quote me!). What does this mean and what can I do about it - I don't have a windows xp disc as the computer is second hand.
Any advice would be gratefully recieved.
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