Problem with laptop

I have a Dell laptop with Windows 7.  For some reason I cannot get further than the desk top, nothing is responding.  Consequently I can't get into Control Panel, or anything else.  I have tried safe mode, which seems to be F2 & F12 (no response from pressing F8 on the laptop, which I use, to take this ancient desktop into safe mode)  But in F2 & F12 I can't find anything that might solve the problem  I remember once before a similar thing happening and I found somewhere on the laptop where I could take it back to an ealier point in time - which solved the problem.  Any idea where I might find this particular function, or any other ideas on how to get the desktop functions on the laptop working again?

Many thanks.