Should I upgrade my CPU[Processor]?

I have a Intel Pentium D Presler 3.00GHz [Not over-clocked + I do not intend to over clock anything]....
I am planning to upgrade basically my whole computer. I plan to buy something from AMD but I don't want something like the sempron...
I heard phenom has glitches on its L3 cache [even though i don't even know what it is] and it takes a lot of wattage...
So maybe an Athlon II or a Athlon 64 X2?

So, should I upgrade? Which out of the althon series is better?

I intend to use this for 'casual' gaming, not like hardcore/demanding games like crysis but not online flash games.

so i dont need to upgrade my cpu?
p.s could you help me with my RAM topic...

It's a fucking Pentium, even at 3GHz it can get slayed by a normal 2GHz CPU.

I would, but you should know that each CPU fits only on a certain socket, meaning that you will probably have to upgrade your motherboard as well. And once you do that you're probably going to need to upgrade your memory as well, reinstall Windows, maybe even get a newer GFX card

Motherboard Specifications, 945GCT-HM (Livermore8) HP Pavilion g3100.uk Desktop PC - HP technical support (United Kingdom - English)
I am going to upgrade my memory from 1gb[512mb each slot] to 2gb... the max is 2gb though
Why reinstall windows? And I'm pretty sure that I am going to get Radeon HD 5450...

Socket 775 (LGA775 / Socket T)
"Socket type: 775
Motherboard supports the following processor upgrades:
Core 2 Duo (Conroe) up to E4300
Pentium D (Presler) up to 960 (3.6 GHz)
Pentium 4 (Cedar Mill) up to 661 (3.6 GHz)
Celeron D (Cedar Mill) up to 365 (3.6 GHz)
Celeron D (Prescott) up to 355 (3.33GHz)"
From my PC manufacturer's site.

I guess i won't be able to upgrade to AMD ¬.¬
EDIT 2: Right, i guess motherboard is the only option.
Got any good/cheap motherboards that fit my case/pc? And how i can do it without reinstalling?
Reinstall = a whole system wipe? I want the programs and files though.... halpppp

If you're going to switch motherboards then yes, chances are you're going to have to either manually change every single driver and the such or just simply reinstall Windows.

With a 100 pound budget I doubt you'll find a decent mobo+ram+cpu replacement. As I said in the other thread, I would recommend you save your money for later.

Well, my budget isn't strict but... you know...
Ebay = RAM + CPU can come cheap.... RAM is like £10-£20 for 2 x 1GB DDR2 PC2 5300...
CPU: Athlon 64 x2/Athlon II x2 £10-£30
PSU: Corsair/Antec 400w at least £10-£30
So yeah... Upgrading the CPU really isn't essential right??

P.S My dad will buy a new computer sooner or later but he probably wont as he thinks 'old' in a computers world is like 5 years/when it breaks down/slows so much. [Right now its like been 2 years]

The only thing I would upgrade is RAM / PSU+GFX. The CPU isn't that important for playing games, especially compared to the role played by a gfx card.

Wew. Thanks a lot!!! You just saved me [a lot] of money :P
RAM + PSU + GFX here we go =D
But i still have to wait till my b'day which is on the 22nd where ill be aloud to get a debit card :P

go for a socket AM3 mobo and a AMD Phenom II X4 athlons are amds budget cpu and that being kind