i strongly suggest this site! it has helped me planned out my computer, but i have done some further research and have switched parts and components. But this is basically a starting guide (establishment) for your computer! http://www.gamingpcbuilds.com/
Your budget is pretty restrictive, and you haven't mentioned what you plan on using this system for: gaming, productivity, etc, but I am assuming that you plan on doing a little gaming, so built this with that in mind. I personally use Intel chips with dedicated graphics, but for $450 that isn't really possible.
MB&CPU combo: ASUS F1A75-M PRO FM1 AMD A75 (Hudson D3) SATA 6Gb/s USB 3.0 HDMI Micro ATX AMD Motherboard with UEFI BIOS with AMD A8-3850 Llano 2.9GHz Socket FM1 100W Quad-Core Desktop APU (CPU + GPU) with DirectX 11 Graphic AMD Radeon HD 6550D AD3850WNGXBOX $191.98
Please note: this does NOT include an operating system....chances are that you will need one, which is another $99ish for win7 OEM.
Also, if you have a microcenter near you, you can likely purchase motherboards & processors for less than newegg's prices.
On the whole, I would spend an extra $200 or so and get an Intel chip with dedicated graphics, but if $450 is your max then something like this is probably your best bet, because at least you get a passable quad core processor and passable graphics...and later on you can add a $75-120 dedicated GPU for considerably better performance.....just bear in mind that this power supply only has 1 PCI-E graphics pin, so won't power the latest greatest cards, but there are plenty in the $100ish range that will be powered just fine.
perfect for a low budget Intel build at an amazing price., get it in combo with a Pentium if you can for an even better deal.
Don't buy it if the price increases to more than 30, it's a great budget board but it doesn't compete with the 39.99-45.00 h67 boards from better brands such as Biostar.
I highly suggest the Sandy bridge Pentium G850 on your budget. It's fast enough that you won't notice it's slower than most of the line up (faster per core than any AMD offering). I've had a great experience with mine (1600x900 resolution pared with a Radeon HD 6750) and play games such a dragon age or supreme commander on ultra without problems. Newer games can play on high.
When you get some more money you can upgrade directly to a quad core i5 if you need to (better to just buy a better computer 2 or 3 years down the line). Motherboard can also upgrade to ivy bridge processors if it lasts that long in your case.
8GB ram is a waste of money with this budget. get a 4GB 2x2 kit (usually ~21.99 on newegg) It's basic stuff without heat spreaders, but whoever heard of ddr3 1333 memory overheating?
Cheap mobo: 14.99 - 24.99 AR
Pentium: 87.99, ~69.99 if you can get it in MOBO combo
4GB(2x2)ddr1333 memory: 20.99
CASE: (any under $40) 40.00
PSU: (corsair cx 450 or better) 35.00, 40.00
HDD: (any under $75): 75.00
so in my estimated build, you'd have spent 271 maximum on parts except your GPU and DVD(I don't use disk drives so I left that out). I'm assuming your resolution is 1600 x 900 or less, if it's greater you can basically throw my post in the trash.. if it's less than you'll have a high/ultra gaming system.
Personally, the maximum GPU i'd buy for my resolution is a HD 7770 (yeay for new goodies) because it's low power to fit in your low end system but can do ultra at 1600 or under resolution.. it's better than my GPU and i'm quite pleased with a very similar build.
That would set you back another 135.00 or so,
new total: 406.00 before tax&shipping.
Yep, just figure out a case and hard drive and see if you have wiggle room in your budget. Don't listen to that last guy, 450 is plenty of money for a gaming build at resolution 1600 or less. 1920x1080 or higher would require more money, however.
also note:: The i3 is a tempting upgrade but it's really not worth it in a low budget system. You're paying a lot more for .4ghz more (2.9 pentium vs ~3.3 for the i3-2100) and hyperthreading. Hyperthreading allows your under-stressed cores (they're both dual core) to take on extra work via the computer pretending it's two cores and giving it two jobs at a time..
when was the last time you played a game that left your CPU under stressed enough to take on another job? benchmarks prove it doesn't help gaming at all, and in fact can cause slightly lower performance because while under high stress the CPU is also trying to fit in cpu time for it's other job..
stick to a pentium and put the extra money in a decent GPU, you'll come out with a budget gaming build to be proud of.