Dual Boot: booting freeze / hang up

Dual Boot: booting freeze / hang up

I had Ubuntu 12.04 and Windows 7 installed in my system and decided to
replace Ubuntu with Linux Mint. In the linux mint installer, I lazily
chose the first choice which is to install over ubuntu, erasing and
replacing ubuntu with linux mint.
After I restart my system when the installation was done, it freezes for
about 10 minutes. It is in the part where you can press a key (DEL in my
case) to enter the bios or the motherboard. Also, I can no longer enter
the bios when I press del.
After that, it continues to the loader(windows) where you can choose the
OS you want to use.
I tried re-installing Linux Mint again formatting the partition myself
(the same way I installed Ubuntu before) but it still freezes when
booting.