What to save textures as?

Going trough all my projectAI textures, some are realy old and look....well....crap ;)I find lots of good textures here but most good once are in 32 bit and i would like to convert them to something smaller, should i use DX1, DX3, rezise? Dont find the need to have AI taking up 3 gig of hdd space :)Best way to not lose to mutch detail (spec the reflection) but still bring down the file size.Sorry for my bad spelling and thx in advance