Make sure you are logged on as an Administrator account when checking your Windows/Tmp folder. If you are not and logged in as a Standard User that folder will be locked on all other User accounts but the Standard User account.
If that fails to work, download the free
LOCKHUNTER utility
(YOU CAN GOOGLE FOR IT!) which should tell you which app or program is holding that folder closed or locked; you can then delete it--it may require a reboot or two to accomplish a complete unlock. From there, you should be able to delete all the folders and files within your Tmp folder. If you cannot, you likely have significant windows corruption, and a full windows reinstallation with a disk wipe clean is going to be in your near future if you want to free up any space on your hard drive.
Also, if Lockhunter doesn't do the trick, it's highly likely that your Hard Drive is failing or has failed. Have you tested it? If not, keep in mind that desktop hard drives are only designed to last 3 years, and laptop hard drives only 2 years!
If you are the original owner of this computer and have never replaced the hard drive in it or paid someone to replace for you, it's very likely that it's failed by now!
If you get to this point, be aware that read sector errors on failing drives often cause system folders in windows to appear locked when they are not, it's just that your hard drive has flaws on it's surface that prevent windows from reading information in the normal locations where windows stores them on the hard drive.
You can take your computer to a local Computer Pro and pay him to replace your hard drive and reinstall W7 on it. Or if you wish to DIY, I wrote an very easy step-by-step Troubleshooting Guide which will allow you to test your Hard Drive, RAM, and other hardware inside your computer, as well as use common software repairs to get your Windows running again. Bear in mind, that Windows reinstallation almost always clears off all kinds of junk including massive Registry entries no longer being used in your Registry by programs you no longer use or have at one point removed.
There are utilities such as CClearner
Link Removed that will help you with this, but not nearly as much as a full drive wipe and Windows reinstall!
Most kinds of problems with Windows can be resolved by a full Windows factory reinstallation; and that will stick better if you don't do the reinstall on failed/failing obsolete hard drives.
Here's the link to my Troubleshooting Guide:
Windows 10 - Unclickable Task Bar
If you get stuck along the way, post back any questions you have. We are here 24x7x365.
Best of luck,
<<<BIGBEARJEDI>>>