try this
Step 1:-
Start your computer in Safe mode.
Steps to start your computer in Safe mode with Command Prompt,
1. Restart your computer and before Windows logon screen appears press F8 continuously which will bring “Advanced Boot†options.
2. Please select “Safe mode with Command Prompt†and hit enter to start it.
Safe Mode is a Diagnostic Mode of Microsoft Windows Operating System running with minimal set of services and drivers.
Step 2:-
1. At the command prompt, type – NET USER Administrator /active:yes
This will enable the built-in Administrator account.
2. Type NET STOP ProfSvc in Command Prompt to stop the User Profile service if you get any error message.
3. This command line utility will bring you back to the login page along with an Administrator login.
Note: - If you did not set up a password when you configured the system the Administrator login will not have a password.
4. Press Control-Alt-Delete key simultaneously to start Task manager.
5. In Applications tab, click on New Task and type explorer.exe in empty box.
6. Now, you will be able to get to Desktop.
Step 3: -
Take ownership of C drive, do the following:
1. Right-click the C Drive and then click Properties.
2. Click the Security tab.
3. Click Advanced, and then click the Owner tab.
4. In the Name list, click your user name, or click Administrator if you are logged in as Administrator, or click the Administrators group.
5. Click on Edit and then put a check mark against "Replace all existing inheritable permissions on all descendants with inheritable permissions from this object".
6. Click OK, and then click Yes when you receive the following message:
This will replace explicitly defined permissions on all descendants of this object with inheritable permissions from C-Drive (C:).
Do you wish to continue?
7. Once the permissions are replaced, click on Ok.
8. Check if you are able to copy, paste or delete any documents now.
Step 4: -
If the above steps fail then you may also want to disable UAC and check if that helps.
To change UAC settings
1. Click Start, and then click Control Panel.
2. In Control Panel, click User Accounts.
3. In the User Accounts window, click User Accounts.
4. In the User Accounts tasks window, click Turn User Account Control on or off.
5. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Yes.
6. In the Security section of the Windows Solution Center page, click Adjust UAC Settings.
7. On the User Account Control Settings page:
1. To disable UAC, move the slider to Never notify, and then click OK.
2. To enable UAC or change levels of notification, move the slider to the appropriate notification option, and then click OK.