My drive has a DVD in it, but it keeps saying there is no disk in the drive.

Make sure all leads that are attached to your cd/dvd have secure connections and are not faulty or just replace them they could be faulty ?
you might have to physically unplug the cd/dvd drive restart your computer this should activate the found new hardware wizard
Click start control panel administrive tools,computer management,device manager scroll down cd-dvd rom drives you might see a yellow question mark ? right click you will have options to update driver,roll back driver,or select properties general troubleshoot, select driver click to reinstall drivers click update driver or uninstall then reinstall if this does not fix the problem it might be a registry problem if you cant see your disk drive in windows explorer
Close all open programs

Click on Start, Run, and type regedit and press Enter
Click on the plus signs (+) next to the following folders

HKEY_LOCAL_MACHINE

SYSTEM

CurrentControlSet

Control

Class

{4D36E965-E325-11CE-BFC1-08002BE10318}

This folder is the DVD/CD-ROM Drive Class Description in the registry. Look for any of the following names in the right hand column.

Upper Filters

Lower Filters

Upper Filters.bak

Lower Filters.bak
If any of the above keys shown in step 4 are listed, right-click on them and choose Delete

After deleting the keys, close the registry editor
Reboot your computer
Open My Computer and check to see if your CD or DVD drives have returned. You may also want to open Device Manager and verify that the yellow exclamation and error code on the CD or DVD drive is gone.
hope this helps