Its normal having HDD got hotter coz all the programs are running in there and so on. You should try touching your processor too
The modem problem. Sometimes you got to believe that there are 'interference' during the connection. It'll work perfectly fine as always if it was a cable, such as fibre optic.
I don't have DVD on my computer though but you know, DVD are slightly heavier running than a CD

It takes quite a lot of juice to run anything. Burning CD's are recommended to close down all programs. Have you ever experience touching your DVD-Rom while its processing?