hi, i recently upgraded my dell 4300 to 1 gig of ram and also added an ati radeon 9550 with 256 mb of ram. i thought this would be enough to run some newer games at fair quality. Most games run alright, halo, tc:e. Games like bf2 open but its pretty painful to play. My cpu is the next thing i was thinking about upgrading. I have been having trouble finding one that will fit. Then again im not even sure what factors effect it. http://support.dell.com/support/edocs/systems/dim4300/specs.htm#1101572
those are the official documentation of the specs.
Field Value
Motherboard Properties
Motherboard ID <DMI>
Motherboard Name Dell Dimension 4300

Front Side Bus Properties
Bus Type Intel GTL+
Bus Width 64-bit
Real Clock 100 MHz (QDR)
Effective Clock 400 MHz
Bandwidth 3200 MB/s

Memory Bus Properties
Bus Type SDR SDRAM
Bus Width 64-bit
DRAM:FSB Ratio 4:3
Real Clock 133 MHz
Effective Clock 133 MHz
Bandwidth [ TRIAL VERSION ] MB/s

Chipset Bus Properties
Bus Type Intel Hub Interface
Bus Width 8-bit
Real Clock 67 MHz (QDR)
Effective Clock 267 MHz
Bandwidth 267 MB/s

Motherboard Manufacturer
Company Name Dell Computer Corporation
Product Information http://www.dell.com
BIOS Download http://support.dell.com
or maybe that could help. Could someone please guide me in the right direction , i would greatly appreciate it thanks

A new CPU may help somewhat, but your R9550 is the weak link. You could have done much better without spending a hell of a lot more.

And the power supply will be the next weak link. What is the wattage on that?

ya, it has 250 watts, but how can that effect game play. I think the video card recommended 350 but It hasn't crashed or anything...yet

You got lucky. When you put a higher end graphic card in there that requires more power the problem will become apparent.

just searched google and found this person:
Dell Dimension 4300 Series Mid Tower PC

Intel P4 Celeron 2.8 GHz CPU, 400 MHz System Bus, 128 KB L2 Cache
512 MB PC133 SDRAM
DVD-R Drive (new)
16x Dual Layer DVD-R/RW (new)
Floppy Disc Drive
2 x 40 = 80 GB Hard Disc Drive
nVidia GeForce 64 MB Grfx with VGA/S-V TV-Out
Sound Blaster Audigy LS 5.1 Digital Sound Card

so im quesiing pentium 4 2.8ghz this is the fastest 400mhz FSB pentum 4 to but the person with that rig is also a n00b and doesnt know if he has a celeron or a pentium 4 but im quessing pentium 4

But a better option considering what your doing is to get a full motherboard and cpu upgrade you could still go t 2.8ghz here is one on ebay:

http://cgi.ebay.co.uk/NEW-INTEL-P4-MOTHERBOARD-INTEL-P4-2-8-CPU_W0QQitemZ180012995710QQihZ008QQcategoryZ131530QQrdZ1QQcmdZViewItem

Pentium 4 3.2ghz @ 3.5ghz
Nvdia4 Mx4000 OC@ 350/500

ok cool thanks

Any old power supply off the shelf is not going to work, and any old motherboard is not going to snug into that case!