Regardless of what anyone says, no one can really answer this question for you. The easiest way to answer it is to learn all that you can about what you are doing. Only then can you make the best decision about what PC is best for you.
I normally suggest something like the following to begin with, but it all depends on what you want to do with your system. The following would be a fast system for just about everything you could possibly want to do at this point in time, is highly stable and doesn't put a dent in your credit card...
1. Asus A7N8X-X ($70-$85)
This is the budget version of the regular A7N8X boards. Don't let that fool you though. All it means is that it is missing a few features, none of which most people would ever use (including myself). By far some of the best on-board sound you can get on a motherboard which eliminates having to buy expensive sound cards and the on-board sound doesnt put pressure on your processor which leaves you lots of room for gaming. Also very stable (so long as you have installed the latest Nvidia chipset drivers).
2. Hard Drives (recommend spending $80-$100)
Hard Drive's are priced very oddly. You can purchase a 20GB hard drive for about $60, yet you can get a 80GB for about $80, or a 120GB for around $90. So, I would suggest purchasing either a 80GB or 120GB Hard Drive. As far as brand goes I suggest either Western Digital, or Maxtor.
3. Power Supply (recommend 350W Enermax $50)
This IS a very important factor in your PC. Especially now with Athlon XP and P4 systems which usually have several fans, CD burner, DVD, etc. The best brand you can buy right now is Enermax. I suggest at least a 350W power supply in any case. If you buy a cheap power supply go for at least 400W, if you go with a PSU such as Enermax, Antec then go for at least 350w. The reason for this is cheaper power supplys don't push the power that they claim to and you run the risk of these causing problems (either the PSU dying alone or taking other components with it). The least that will happen is a loss in stability. The worst is losing your PC.
4. Video Card (recommend ATI Radeon 9600 Pro or higher ($150+)
ATI is ahead in the graphics card race at the moment and Nvidia is lagging behind. The ATI 9600 Pro supports DirectX9 which you will soon need for gaming (although so does the 9500 Pro), but the 9600 Pro will play any game that you throw at it. It is "said" that the 9600 Pro will also play Half Life 2 with not much of a problem at lower resolutions (my guess is 800x600, and *maybe* 1024x768 but that may be pushing it -- we won't really know until HL2 is released). If you plan to play intensive games such as HL2 I suggest you wait until it is released and purchase a lower end card at the moment. Or you can go with the ATI 9800 Pro for about $305-$380 and you shouldnt have a problem (just don't expect to run at insane resolutions).
5. AMD Athlon XP 2600+ ($95)
This processor (along with a decent video card, and 512MB) will run any game that you throw at it right now. I have one myself and I am very satisfied with it. I do a lot of gaming, graphics, video editing, sound editing, etc with no problem whatsoever.
6. RAM (recommend 512MB of PC2700 or higher)
If you get an Asus board then you should go with Corsair RAM. If you plan on using dual-channel RAM for about a 0-5% increase in performance (depending on the motherboard that you use) then you should buy a motherboard that supports dual channel and 2 exact same DIMMs. In other words it is a good idea to get a Twin pack of Corsair (Twin-X). Some motherboards are designed now with capability of RAM performace the same as dual-channel while using and being designed for single-channel.
*You dont need more than 512MB at this point in time unless you plan on doing video editing, graphics, etc. Gaming doesn't require anything over 512MB. It relys more on other things such as your processor, and video card.
Hope that helps.