Hello Alakim Welcome to Neosmart Technologies.
Before your PC boots you should see a screen that says hit F2 or Del for setup. That will get you into your BIOS. Go into the BIOS and check your boot order. IT will read to boot from your CD/DVD driver before your hard drive. Just move that down to after your hard drive and that should prevent this from happening.
The only reason why we leave it that way is so when we want to boot from a CD/DVD that option is there. Like when we have to re-install or something like that.