I've got Hundreds of GB's worth of RAW files.
I don't delete ANYTHING.
I started a new Lightroom library on a new installation of XP to keep everything tagged and orgonised.
My Advice? Buy a few 500GB hard drives
They are the best "bang for buck" in terms of Storage to Price ratio.
Canon EOS 5DmkII + BG-E6 + Canon EOS 40D + BG-E2N + Canon EOS 33
Canon 17-40 F/4L
USM + Canon 24-70 F/2.8L
USM + Canon 28mm F/1.8 USM + Canon 70-200 F/2.8L
USM IS + Canon 85mm F/1.8 USM
Canon Speedlite 580EX II + Canon Speedlite 540EZ + 2 x Nikon SB-80DX
Cactus V2s Wireless Trigger - 5 x
Cactus V2s Wireless Reciever