The mobo you're using needs DDR3 ram. (As most i5 processors do, afaik.)
It should (I say "should" with a lot of caution here.) fit in your case. You may want to look at modding it so you ca allow for more airflow if you plan to overclock. (Or get a watercooled system, I've seen a number of them.)
I would advise you to find a HDD with 7,200 RPM. I had a 5,400 Green Drive and it made loading times uncomfortable for games and other applications.
I've decided to build a custom desktop that will be used for both gaming and rendering. I'm also going to overclock the CPU to maximize its potential. However, I'm not sure if the parts I used 1) will fit in the case I have picked and 2) are compatible with each other (ie, power cables, etc). Can anybody please help?
Case: Antec 300
CPU: Intel i5-750
Cooler: Cooler Master Hyper 212 Plus
GPU: Diamond Radeon HD 5870
RAM: OCZ DDR2-800 4GB (2 x 2GB)
PSU: Cooler Master GX 750W
HDD: EcoGreen F2 5,400RPM 1TB
Mobo: Intel DH55TC
Disk Drive: Samsung 22x DVD