im confused. I have had a look at an Athlon 64 3400 and it showed a base setting of 2.4 GHz? a LOT of retailers have been notorious for supplying the wrong AMD processor as they get mixed up with model codes, it might be worth checking out. you might have an Athlon 64 3200+ which has approximatly a 2.2 GHz base setting...

As far as clocking is concerned you need to specify what cooling and also other hardware such as the motherboard ect.. so that anyone can get a genereal idea of how far and how stable the system can be taken. Most AMDs are remarkably stable at higher clock speeds. You can buy an Athlon 64 2800+ and clock it to 2.4 GHz; with sufficient cooling you have an instant Athlon 64 3200 for Athlon 64 2800 money i couldnt say if the setting you said is stable or not, at a guess yes as its not much of an increase but at the end of the day it is your system and i dont want to give any false sense of security towards you frying anything!

ok, first umm amd has two 3400+ models
one (mine) has a 1MB L2 Cache and 2.2Ghz
the other has a 512KB L2 Cache and 2.4Ghz

I brought my cpu back down to 2.2Ghz , unless someone can tell me if they are 100% sure I can run it safely then I won't overclock it, my temps did not go up they were at 42C

Clawhammer: 2.2Ghz, 1Mb of L2 cache.
Newcastle: 2.4Ghz, 512Kb of L2 cache.

ah ha! i only found one architecture. If the temp didnt change much then it could be a safe bet. reducing it a few degrees would give you a safety margin though. What method did you use to cause the increase in the first place? im curious >> i havent seen the Claw Hammer 3400+ before! i know of the following close to 2.2 GHz:

Socket 754 Athlon 64 3400+ Newcastle (2.4 GHz, L1=128, L2=512)
Socket 939 Athlon 64 3500+ Winchester (2.2 GHz, L1=128, L2=512)
Socket 939 Athlon 64 FX 55 ClawHammer (2.4 GHz, L1=128, L2=1024)

i have a LANPARTY motherbaord it has built in overclocking in its BIOS

ah yes ive seen those boards. It should be stable, if im correct i believe the LANPARTY has multiple bios profiles? if it does then at least you have stable settings to revert to should things start to get lairy. 2.2 -> 2.3 with a overclocking friendly motherboard seems ok to me, but in the end it is up to you. I havent much experience with Athlon 64 CPUs so im not positively sure about the higher end CPUs potential as most examples i have seen have been lower spec 64s tuned to higher spec, and only one example of a 64 3400+ (Newcastle) going up 3-4%...

have the cpu running at 2288 which isnt much jump from the 2210 and I like the results im getting Ill just keep it at this speed.

3400+'s come in two flavours, Clawhammer(2.2GHz, 1Mb L2) and Newcastle(2.4GHZ, 512Kb L2). I think there may be another Clawhammer variant but I'm not sure, they do come in two steppings though.
I have been overclocking my Newcastle 3400+ at ~2.6GHz (217x12) for weeks and it has tested in prime95 stable for hours. (and hours).
My main BIOS settings are as follows:
vCore = 1.65v
HTT/FSB = 217
multiplier = 12
vDimm = 2.8v
RAM divider = 1:1
Prime95 seems to be the "community" standard for stability testing, it has a torture test you can run (options >> torture test). If your cpu is unstable it will usually fail within 15 minutes or so, but 4hrs plus seems to be a good indication that your cpu is stable.
If the program fails, it will stop. You can get it here.
The Athlon 64 have a max temp rating of 70 degrees, if you reach it, the pc shuts down automatically, but I wouldn't recommend running anywhere that speed. Mine runs ~40 degrees idle and ~48 degrees under load at the above mentioned settings with a 3rd party heatsink and fan. (Even though I think it's a POS, the HSF, not the cpu).
I can get a 10% increase (2640MHz) running a vCore of 1.72 but the temp increase is not acceptable, so I'll have to wait until I get my watercooling setup to find out just how fast the cpu will run.
I'm assuming you have the stock heatsink/fan from AMD? As long as you've not raised the voltages, you should be fine as long as it tests prime stable.
If you are overclocking, turn off Thermal Throttling in the BIOS, it interferes with the overclock, BUT, if you are running the factory bios shipped with your Lanparty, there may be a problem when you turn it off. There are some more factory bios's that Oskar Wu (board designer) has released that fix this issue.

well when I upgrade the fan and heat sink to a very good one, I will OC the cpu to like 2.4 or 2.5 and test it, for now its staying at 2288Mhz