What Hardware creates the computer bottleneck?

What hardware typically slows the system down the most. Is it the hard drive., motherboard, memory, graphics card, etc.

I am running

2.4 P4
512 RDRAM PC800
2x80GB 7200 RPM 8MB Cache
ATI All-in-wonder 9200
DVD-RW
DVD-ROM
No-USB 2.0 (purchased a card to replace- in mail)

I was wondering if a 10,000 RPM would speed the computer up a lot.

Where the bottleneck is depends on what you are doing. For games, the graphics card is often the limiting factor, particularly at higher resolutions. A faster hard drive would increase system performance for many applications, particularly those that access the harddrive, like program installations, boot up, and some games.
If you're thinking of gaming applications, I would upgrade your video card before upgrading the hard drive.

At 10,000rpm Drive may help, if you get one grab a SATA version. I'd suggest "Western Digital Raptor 74GB 10000rpm SATA". To my knowlegde thats one of only 2 HDDs that can achieve 10000rpm without SCSI.

Independent hard drives cannot transfer data at or even near the bus speed of a computer. Consequently hard drives are the bottleneck. Even combined into arrays (RAID's) they can't keep up with the bus speeds. This has been a problem for years. Solid state hard drives connected to the RAM bus could perform at or near bus speeds (in theory).

Karsh indicated a video card can create a bottleneck. This is correct as some games, and other video, process faster than the video cards allows. (i.e., Game plays as 32 frames per sec, card only supports 24 frames per sec.)

data4t

I would say rather that some games and video require more processing power than the video card has. The video card will render as many fps as it can. 30fps is considered the minimum playable frame rate, and games like far cry and the upcoming Doom3 and Half-life 2 with high detail settings will tax even the best cards to the limit. If the detail is too high, the card can't render enough fps, making the game "lag".

A frame rate above 85fps is not very useful, as 85hz is the max refresh rate on many monitors. The card may be able to render more fps than that, but it won't result in increased performance.