That is a good motherboard and you also picked a case with a respectable power supply. The Seagate hard drives are not the fastest ones, but they are very quiet (I use some of them). What brand and model of video card did you buy?
The CPU and memory are probably what your friends are talking about.
1) The Celeron 2.4GHz is not nearly as fast as a true Pentium4 (see
this review for some examples).
2) You will get the best performance if you use two matching memory modules, and PC3200 will be best. The motherboard is designed to combine the two modules into one double-size data pathway, called "dual-channel." It can operate in single-channel mode, but it will be better in dual-channel mode, and it will be best when it is dual-channel PC3200 (also called dual-channel DDR400).
It is probably powerful enough for student work and some of the games, like HalfLife/Counterstrike and Unreal Tournament, but if you are going to play the newest games, you will get a lot more power if you upgrade to a Pentium4 2.4C and dual-channel DDR400. Notice that in the article, the Celeron is being tested with dual-channel DDR400, and it is still slow then.
Also, you will probably get better performance when you upgrade to 512MB of memory too.
I hope that helps. Welcome to the Forums
Indradjy 
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