MESSING WITH SYSTEM FILES IS NOT FOR NOOBS

1. Doubleclick takeownership.reg to install
2. Take ownership of explorer.exe in C:\windows by highlighting explorer and any other item, rightclicking and clicking take ownership
3. Rename explorer.exe to explorer.exe.bak
4. Copy new explorer.exe
5. Logoff\logon

Additionally, if you still can't replace it. Right click explorer.exe in C:\Windows go to Security Tab, click Advanced, click Users (User-PC\Users), click Change Permissions, again click Users and click edit, then click Full control. And then click OK, OK, Yes, OK, OK.