computernoob1

I have already posted here concerning the high temps of my CPU and now I want to make sure they are alright.
My CPU temps when idle are 36 C to 41 C, mostly stays around 37 C - 39 C (Core 1) and 27 C to 32 C, mostly stays around 31 C (Core 2) (Don't ask me why there is a huge temperature difference, I have no clue) and when I am in an online game (FPS from 2004 : P) they stay around 47 C to 53 C (Core 1) and 39 C to 45 C (Core 2), and as soon as I come out of oblivion it is at 49 C (Core 1) and 42 C (Core 2).
Are these temperatures okay?
I still have not gotten that CPU fan seeing as my CPU is old and they don't even make my socket anymore and in a year or two I will buy another CPU but I am looking into a case fan but the thing is I don't know how many mm my fan is, can anybody help me with this? : P

In case you are wondering I got my temperatures from Core Temp

EDIT: Or should I not bother with the case fan and just buy another case?
This is the case I have now (http://ecx.images-amazon.com/images/...500_AA280_.jpg)

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CPU - AMD Athlon 64 X2 Dual Core Processor 4600+ 2.4 GHz
GPU - ATI Radeon HD 3870 512MB
PSU - Antec 550 watts
Motherboard - ATI Radeon XPRESS 200P RX480-A
HDD - 320GB Sata
RAM - 1.5GB DDR
OS - Windows XP Professional 32-bit SP3
With Harmon Kardon Sound Sticks & a Logitech headset for gaming