Hi,
You can delete all the "Temp" files. But, some of the temp files will be in use, by some application, in that case you can not delete those files. Instead of searching for temp files manually, you can use applications like
CCleaner,
CleanUp! etc. Download and install them, and run them to clean junk files. It's better to run these to tools in SAFE mode, so that those "in use" temp files can also be deleted.
You can tweak these tools to clean more thoroughly, run
CCleaner, click "Options" button and here go to "Settings" tab and uncheck the option "Only delete files in Windows Temp folder older than 48 hours". Click "OK" to exit from the Options and click "Run Cleaner" to start cleaning. Run
CleanUp!, click "Options" button, move the "Quick Setup" slider to "Thorough CleanUp!" and click "Yes" for the warning message and exit from Options. Click "CleanUp!" to start cleaning. After cleaning, click "Close", and choose "Yes" to restart the PC.
Unsolved 
