Not enough memory!

[netibiza]

sometimes when I am downloading progs ie Eastenders, it says "not enough memory" so It won't download, then sometimes it says "clear some?" and I agree and it gets rid of java (!) and all works ok. Today nothing would work until I removed all the seeding ones which I shouldn't do as the ratio wasn't high enough. Can anyone tell me in simple terms please how to clear some memory ( I've had an extra one put on) withourt removing important things. Many thanks.