I'm having problems reinstalling Ubuntu Desktop with a dvd?

I have an Acer aspire laptop and I've already gone to bios and changed to legacy UEFI and made booting from DVD/CD first priority.
I installed ubuntu desktop 14.04 64bit with LVM and encryption which I am considering to have been a bad choice because I'm having a lot of problems restarting/booting the computer and I have to discoect any usb devices during booting and it always takes me to the grub2 menu and if I simply choose to boot Ubuntu then it gets stuck on a black screen. I need to either hit shift directly after choosing Ubuntu in the grub2 menu or press 'e' on the grub2 menu and change the letters 'ro' to 'rw'. When doing either of these methods, it is random chance that the computer successfully boots, sometimes I need to do this many times before it finally takes me to the PW field to decrypt the disk.

That's why I want to try reinstalling without LVM and encryption incase this is what is causing the problems.

But if I put the DVD that I bued Ubuntu to into the computer then at booting I get stuck on the first screen which is the Acer logo and a small text "Press F2 to enter settings.." F2 is where you go if you want to reach the bios etc. but it doesn't matter what I press, as long as I have the dvd inserted to the computer I'm stuck on the acer logo screen.

I hope that someone will be able to help me