Incremental backup querey

Hi folks
Please excuse me, but I am one of the band of ever increasing Silver surfers.

I have just reformated my PC, installed my basic programs, done a back up with Acronis True Image, added a few more programs, decided to do an incremental back up. was informed that my first incremental back-up would be a full back-up, which went OK.

Question is do I need to keep the back-up of my basic programs I did? or can I now delete it as the first incremental back-up is also a full back-up.

If this has been answered elsewhere I apologise.