Thank you XebozZ... I found this thread very useful after my Samsung Galaxy S2 screen was broken and I could not access my data via my PC as the screenlock was activated.
I would like to add some more detail as it took me some time to activate the factory reset. Note the factory reset removed the pin but the user files such as photos, videos, music etc were still available.
I believe the timing of the button pressing is critical to get in to the Recovery Mode.
1.Remove battery and re-insert to be sure phone is powered down
2.Press VOL-UP, HOME & POWER buttons together (pressing POWER last) for 1-5 seconds (you may have to perform several iterations 1s, 2s, 3s... 5s to get timing perfect)
3.Wait 10 seconds to be sure you are in Recovery Mode
4.Press VOL-DOWN x 2 (to get to wipe data/factory reset)
5.Press HOME (to select wipe data/factory reset)
6.Press VOL-DOWN x 7 (to select Yes - delete all user data)
7.Press HOME (to complete erase)
8.Wait 1 min to be sure erase complete
9.Remove battery and restart phone. Check connection with PC via Samsung Kies or similar.
This eventually worked for me so keep the faith and be patient.
FYI I verified the recovery menu options by searching through Google Images for "Samsung Galaxy S2 recovery mode"
Mine was press down button 3 times, and use power button to make selections. Just to help someone else out. Verizon white s4...