lagging only on one computer

so... i have two desktop computers, both connected to the same internet (not using a router), and both having a core 2 duo processor with 1 Gb of ram. the first one is running maplestory completely lagless. the second computer is having major lag, most noticeable on times when the server is very busy (e.g. in 2x exp events, one computer is running maple fine but the other one gets into a huge lag as soon as i log in and disconnects after 30 seconds).

i tried creating a new user account on the lagging computer, and disabled almost every process\service i could (except for drivers, which i dont know how to stop). that produced much less lag, but still didnt completely fix the problem (my original user account didnt even response when the server was busy, but this account responded with an about 5 seconds delay). i checked my internet speed on both computers using speed test sites, and on both of them it is exactly 1.5 mb. maple's ping (shown using alt+f12) is also the same on both computers, ranging from 200 to 300.

im going to try reformatting soon but i want to know if there is any more simple way to detect the problem.

A friend of mine had a similar problem. His brother's computer ran maple perfectly but his own brand-new computer ran it like crap. After trying everything they could think of, they finally took a graphics card out of another computer they had and put it in his. Maple worked perfectly afterward.
So have you tried getting a new graphics card?

RAM or gfx card, with gfx card being the easier one to get ahold of and install.

its internet lags, not graphic lags. its not that my screen is stuck, its that it takes me 3 seconds or more to use a pot or a skill.

it prob is the graphic card or that you use vista

I have a similar but more stupid problem. Characters level > 40 lag a lot but characters < 40 run lagless. Yes, I've tested this out.

Try checking the DNS
Also, try trace route from your system to the MS Server?