There are many sources for laptop hard drives available on the web. The one I have used frequently is
http://www.drivesolutions.com/
They are reasonably priced and stand behind their products. However, if you know if your internal drive is a SATA or IDE, you can find bargains all over. I would suggest purchasing a USB Universal Data Transfer Kit (see
http://www.drivesolutions.com/cgi-bi...id&itemid=a8.1) so that you can easily create a clone of your internal drive and/or use it as an external, should you so desire. Most laptops will support internal drives up to 500 GB and many have two bays and will support 2-500 GB (HP, for example)
I think your next step is to research what you have in your laptop already. Most hard drives can be removed with two screws. Simply looking at the drive will indicate if it is a SATA or IDE. Some laptops, such as early HP's, use an IDE drive with a SATA adapter. If you are still having difficulty, RSVP with your laptop info & I'll try to help.
DC