Uninstall windows 7?

[bel]

I have a W8 Pro bought about a month ago with windows 10 installed.
I occasionally have a message come up asking me if I want to revert to Windows 7.
I also notice that of the 30gb memory, 28 gb is already used up although I haven't downloaded anything except antivirus and antispyware!
Is the old installation of windows 7 using up the memory, and should I uninstall it?
Help appreciated!

 

[ChrisM]

Hold down the Windows flag on your keyboard and then tap the "E" key.
Windows Explorer should appear.
Scroll list on left until you see THIS PC and expand it if necessary
Right click on the C: drive, select Properties
Click on the DISK CLEAN-UP button, wait for initialization to complete
Click the CLEAN UP SYSTEM FILES button, the one with a shield on it. If asked, confirm you want to continue, wait for initialization to complete
Select (tick) any large entries that you definitely don't need, then click enough OKs and confirmations to make it all go away. This should recover a few Gb of space hopefully.

 

[bel]

Many thanks - did this and I now have 12 GB free!