Can I get some help in assembling a new computer?

[Kunal Saini]

Its more like replacing old parts with new ones.. I am using my old Compaq Presario SG3550 case and the CD Drive that came with it. I am.buying a new motherboard. This is the stuff I am buying
Gigabyte GA 78lmt s2pt
AMD FX 6300
Corsair Vengeance 4GB DDR3
Corsair 450w PSU
Nvidia Gtx 750
Even all this stuff is pushing my budget a little as my parents dont care much about gaming. I will play on a 1440x900 monitor so I dont nee much though.
However I have some.concerns.
1. The motherboard is a little smaller in lenghth than my current one 204mm instead of 264mm but form factor is micro atx same as my case , so will it fit?
2. I wont overclock so I wont need any thermal paste right? Would the preapplied pasre on srock cooler be alright?
3. I am keeping my old Sata Hdd. After changing motherboard, I would need to format the whole.hdd or just the C drive for installing new window?
Please help me out. And on the side note, will it be fine i I use fx 4300 in place of 6300? Would there be huge difference?

 

[Ironsounds]

Hello... 1) Yes... form factor will have matching holes.
2) Yes... pre applied will work fine.
3) Use The WIN install DISK and chose "Custom Install" "Drive options" to allow a Format/New install on the C:\ Partition only.

http://www.cpubenchmark.net/cpu_lookup.php?cpu=AMD+FX-4300+Quad-Core
http://www.cpubenchmark.net/cpu_lookup.php?cpu=AMD+FX-6300+Six-Core

 

[theunliked]

If both the case and the motherboard is micro-atx, it will fit.
The preapplied paste will work fine, but the temps will be a bit higher than aftermarket thermal paste. (probably about 5-10C difference).
And no, you don't need to format the whole hdd. Just install windows on it. After installing a clean windows, you will find a windows.old folder in the c: drive. You can just delete that.
The new cpu will be better, but not by a big difference. I would suggest getting the fx-8350 and then overclocking it slighty. A good tube of thermal paste only costs $10 really. As long as you don't overclock it too high, you should be ok with stock cooler.