I just bought a WD MyBook and i had to format it and when i did that it erased all the files that came one it when i bought it. Thats not a problem is it?
No but buying a Western Digital EHD may have been. WD EHD's tend to be pretty problematic with Macs, I'd recommend returning it and getting just about any other brand. WD's internal HD's are fine but the enclosures they make tend create a lot of problems, they're cheap which is why most people buy them.
Also you should consider running Software Update to get to 10.6.6.
Ok thanks for the advice. The main reason I need an External HD is because i do alot of video editing and stuff like that, could you recommend any Hard drives that work best with that sort of thing?
I use Lacie Quadra d2's, I have 4 of them. However I also think OWC (www.macsales.com) Mercury Elite Pro line and G-Tech G-Drive series is also very good. Any of those 3 would be ideal for video editing where speed is important.
I'd suggest that you seriously consider one with Firewire (rather than USB); especially since you intend to transfer larger video files, etc. Firewire will be so much faster copying your files over. Roger's suggestions are excellent; I have two LaCie's myself.