It's real easy. Press "Alt F10" at the same time, as the computer is beginning it's boot process, Obviously w/o the brackets.
Thank You So MUCH for this answer. Ricky_Critic obviously doesn't know enough about different brands of computers to know that Aspire One's don't come with cd/dvd drives or repair discs to solve this problem that way.
The Alt+F10 trick is even new to me as I have only just begun working on netbooks with no cd/dvd drives.