I had two Windows desktop computers and two Windows notebook computers before I switched to Mac OS X in 2004 to an iBook G4, which was the most stable and durable (water damage to the screen and several falls) computer I have ever owned.
I now have a 2007 20" iMac with a C2D CPU running at 2 GHz, 4 GB RAM, an ATI Radeon HD 2400 GPU with 128 MB VRAM, and upgraded to an SSD with 60 GB capacity, which makes it still fast enough for more than daily use (I can edit HD video, properly transcoded, just fine with it).
I also have a 2009 17" MacBook Pro with a C2D CPU running at 2.8 GHz, 8 GB RAM, an Nvidia 9400M IGP with 256 MB shared RAM and 9600M GT GPU with 512 MB VRAM, a 120 GB SSD and 500 GB HDD inside it. It can do all the things the iMac can do, just faster and with less hangups, though Safari proves to be a bitch lately, letting the MBP panic quite often.
I also have several external HDDs, from 500 GB 2.5" HDDs in USB enclosures to 3.5" 1.5 TB HDDs connectable via Firewire 800 or eSATA, I guess 15 to 20 TB at all, though I backup my photos and personal video footage twice, which takes up 3 TB (including the backups).
Both Macs run Mac OS X 10.6.8 Snow Leopard, as the newest Mac OS X 10.7 Lion is not for me, it is to iOS-ified, which makes buying a new Mac (eventually I have to get a new computer) complicated and I ponder about building my own Hackintosh when it comes to that.