mac powerbook g4 start disk full?

[what..the?]

I keep getting pop ups on my laptop saying "my startup disk is full and to delete / clear some room' I am stuggling to process stuff in imovie as a result too so it is effecting my productivity.

I however havent got a clue what the start up disk is?? Or how to clear / clear delete stuff?

I have gone into 'system prefs' and clicked on a logo labeled 'start up' up then the laptop screen went dark and I was asked to restart my laptop by pressing an holding the on/off button.

Please could i have some help from a mac user in the know, many thanks.

[Myriad2112]

Startup disk will be the boot drive, usually the only HD on a laptop. Just dump everything you can and resart.

[fo3nix]

It's the hard drive inside your mac.

You have too much stuff on it (likely if you're playing with iMovie).

Take stuff off it.

Or buy an external hard drive and put stuff on there.