Take Ownership
Right click on winsxs
folder, Properties -> Security tab -> Advanced -> Owner tab -> Edit -> select your username, check 'Replace owner on subcontainers and objects' -> OK
Add Permissions
Right click on winsxs
folder, Properties -> Security tab -> Edit -> select or add your user name -> check Full Control under Permissions -> OK
Propagate Permissions
Right click on winsxs
folder, Properties -> Security tab -> Advanced -> Change Permissions -> check 'Include inheritable...' and 'Replace all child...' checkboxes -> OK
The folder is under your control now, so you can delete it and its content.