Win 7 Problems With Booting Up

I've gotten the Windows 7 RC 7100 x86 iso burned to a DvD. I have a spare HDD (30gb). I unplugged my main (XP) HDD so I wouldn't have an conflicting problems (if any) during the install.

I put in the CD and rebooted. I booted from the CD and went through the install process. It all went well, no problems, it made its main partition with the reserved system partition on the HDD.

The computer I tried putting it on has:

AMD Athlon 64 3200+ - 2.2ghz

1.5gb RAM

nVidia GeForce 6600 Graphic Card

[eMachines model: T6209]

After the initial file copy and 'expanding' it says I have to restart the computer to continue. So I did. Starts up like normal, then all I can get a glimpse of on the screen is "Loading ..." - dunno what else it says

then I get the Windows Boot Manager telling me "Windows has encoutered a Problem communicating with a device connected to your computer.

File: BootBSD

Status: 0xc00000e9

Info: Unexpected I/O error occurred.

I got frustered cause this happened multiple times (kept reformatting, then reinstalling) so I put it in a computer and was gonna intend to put windows 2000 on it (Pentium 3 1ghz Processor w/ 328mb of Ram)

Once in that computer Windows 7 started up normally and finished the install process and works on that computer. Which is below the requirements.

I have another eMachines computer [Model: T3256] that I put the HDD to see if maybe its a eMachines type problem or not. Windows 7 booted up just fine on that computer too (AMD Athlon XP 2.2ghz Processor. 1gb Ram. AGP graphic card {ATI Radeon 9600})

I want to know why I cannot get Windows 7 working on the computer I originally wanted it to be on. Theres no real difference between my eMachine computers besides one has FireWire port (which I disabled during the many installations) and 1 PCI-Express slot.