|No RAM has nothing to do with it at all.|
If you want to prevent someone from accessing data on the hard drive after you have sold / passed on your laptop then you have a number of options.
The options will depend on if you have the original recovery partition that came with the laptop that allows you to recover the system to a factory fresh state.
If you do have this recovery partition then you do NOT want to delete it as it provides the new owner with a licensed original factory fresh install.
For the case where you do have a recovery partition, and you want to retain it, then you can use Active@ Kill Disk - Hard Drive Eraser available from http://www.killdisk.com/ to securely delete data from all the other partitions except the recovery partition.
For the case where you want to wipe the hard drive completely including the recovery partition then download from your hard drive manufacturers website their hard drive utility tool (e.g. seatools, data lifeguard, powermax, etcetera). You can get information for most of them from http://www.tacktech.com/display.cfm...
Create/Write a bootable CD for your hard drive manufacturers utility and run it. Use its low level format feature to write zeros to every location of the hard drive. At the end of this you will have NO DATA on the hard drive and it will be like a factory fresh hard drive. This is the MOST effective way of cleaning a hard drive short of taking a hammer to it.
☺ When everything else fails, read the instructions.