IMO, the USB, using one of the popular installers - is a waste of time - unless you don't have a Optical Drive Burner. Now, with some help and prep, you can do a Full Install to a USB. This will be like having it on your Hard-Drive, and therefore be able to save files, software, updates etc., anything you would be able to do with it installed to your pc, albeit slower. This will also allow you to get some experience with the LinuxMint Installer. Then at some point if you like all this linux stuff you will be more prepared to install to your pc on HDD.
Doing this is simple/usually but you will need help so not to Delete your current OS.
Unsure about what would make the DVD Boot experience smoother, although it is slow to boot, which is normal. After your Optical Drive is set to boot from you can just leave it that way. If the LiveLinuxDVD is in, it will boot from it, if not then it won't, it will just boot from your pc's OS. Just need to be careful as to what else you put in there and boot from, may need to change it back for other stuff.
When you boot up linux again, open the terminal and paste this Command: inxi -Fxz >Press Enter and post the outcome here. Nice little feature of linux. It will tell us some basic info of your computer but no personal info. These guys will really need this info. to better help you out.