43C isn't hot for computer components, however with hard drive it could be different. I'd run a fan thru the front intake to be safe.
Provided you mean Lakeport 945G as there is no 1945G, the supported processors are below:
Pentium 4, Pentium D, Celeron D, Core 2 Extreme, Core 2 Duo
Power supply and Motherboard size (form factor) are moreso related to your case size.