When I left click, the hourglass shows and it takes a while for the droplist to show up. I get a (not responding) as well while browsing through files too. Anyone know what's wrong?

Which OS?

laggy left click is because of your saggy left nut

and are you sure it's not right click? and have you tried rebooting?

your OS and PC specs might help us figure out what is wrong

If Windows then it's probably a slow third-party shell extension. Google for autoruns which can disable 'em (Under the Explorer tab, make sure you only disable third-party stuff or Windows could break).

Look under the "ContextMenuHandler" groups (there's about 5), as those are the right-click menu stuff. You can try disabling a few third-party ones then you should be able to immediately try right clicking to see if the problem has disappeared.

Autoruns doesn't show ContextMenuHandlers that only apply to specific file types or specific folders (like the desktop).

"DragDropHandlers" apply to drag and drop menus, fyi. "CopyHookHandlers" is a general drag-and-drop handler.

Ctrl+alt+del

Processes

Look for whatever is chewing up the most mem usage and kill it (with the exception of explorer.exe) Could be a number of things. New anti-virus? Anti-virus automatically updating? Some kind of malware? Run the usual scanners just to be safe. As always, reboot.