Was the conficker just an April fools joke? Or is it still in action. My computer has been down all day, and now its working again. Very confused.

Its an April fool virus

No joke at all, but completely serious and potentially the largest Botnet ever.
Think Terminator 3 ;)

Its real and potentially the biggest ever.

Microsoft has offered a $250,000 reward for any information on the creator.

Here's a good synopsis of what happened: Conficker D-Day Arrives; Worm Phones Home (Quietly) - PC World

No,It's a virus/worm. Also Known as “Downadup” infection.it can infect your computer and spread itself to other computers across a network automatically, without human interaction.so please update your Anti virus software on your computer.