i'm not very good at CPU model. would anybody tell me if this Intel Pentium Dual Core T4400 works faster and stabler than my old Intel Core 2 Duo T5500 (1.66Ghz)?

You can find CPU performance comparisons at http://www.cpubenchmark.net/cpu_list.php

Normally, Dual Core is older technology than Core 2 Duo. Also, the workload matters when comparing CPUs. If you think a C2D is slow, you probably have too much crap on your system, not enough RAM, low end graphics or a virus. There's only so much a laptop CPU and integrated graphics can perform.

Using this model right now / own it / love it / bought it straight from Dell Pre-Black Friday for $450.00 shipped / took a while to get rid of the Dell bloatware crap / but once i did runs nice / just a basic laptop / the web cam runs at 1280x1024 which is nice / Battery life is average / only con is a "G" card instead of a "N" / other than that i'm very happy

thanks, #2. i'm not complaining that my laptop runs slow. but just want to get a laptop with better graphic card. mine is GMA 950 which can't support many games.