I have a pix515E that was working fine. then it got in rommon a few days ago and now it shows nothing in hypertrm window except for that in the attachment. what is wrong with it and what can be done, can you tell?

I got pix515E which is in rommon and needs IOS upgradation. can anyone quickly send me the link? it's urgent. thanks.

I just wanted to know - where is the basic difference in applicability of PIX and IDS? can I replace IDS with a PIX? my question is simple, where specifically we need PIX and where IDS?