While the CPU most directly influences overall PC performance, memory and HDD influence it as well. The influence of the performance of HDD on users has increased rapidly because of the following reasons:

As the Audio & Visual function of the desktop PC has expanded and become more important, the dependency on virtual memory has increased. Virtual memory is the temporary storage area where high-volume files are kept. These high-volume files are too large to be stored in PC memory while running a program. Usually, it is the place where high volume graphics or audio/video files can be temporarily stored. (In Windows 98, Windows Me, Windows NT and Windows 2000, virtual memory allows the computer to use hard disk space as random access memory. The computer uses virtual memory to augment the normal RAM that is installed on the computer.

Source : Microsoft Homepage) Consequently, the work efficiency of users is influenced by the data transfer rate of the HDD when using a program with a high dependency on cache memory, like most graphics software. For example, with the program Windows Movie Makers that is included in Microsoft Window XP, users can edit or save a file easily without professional knowledge of software. However, as this operation requires the input/output of tremendous data from HDD, dependency on performance of the hard drive is significantly increased. In addition, as high volume files are also frequently used for other applications such as Powerpoint or Internet, the dependency of the end user on virtual memory of hard drives has been significantly increased as well. The resulting inconvenience of end users with much longer waiting times has also increased.

As the volume of programs become larger and more complicated, the numbers and times of loading have increased drastically. Additionally, for Game programs, loading tasks may be repeated occasionally as per process, the data transfer rate of the HDD is therefore influenced significantly on PC usage.

While RPM, access time, interface, and cache memory are all factors that determine the performance of the HDD, the most important factor is RPM (revolution per minute of the disk). As disk revolution speed increases, the internal data transfer rate (data transfer rate when reading or writing data) increases directly as well. While access time indicates the time it takes for the Head actuator to access the place where specific data is stored on the disc, it also significantly influences the performance of the HDD.

The interface acts as the bridge that transfers data between the HDD and the PC. The most important algorithm for data transfer is that, the data transfer rate of the interface should always be higher than the internal transfer rate of the HDD, so as to avoid bottlenecks of data transfer. The transfer rate of an ATA-6 (UDMA100) interface currently used is 100 MB per second, which is enough to prevent a bottleneck for a 7200 RPM HDD with a maximum of 55 MB transfer rate per second.

While Cache memory, as the place where data is stored before it is written to disk, or the temporary place to transfer data which is read from disk to PC, may be sufficient to prevent the bottleneck of data transfer depending on the internal transfer rate of the HDD, cache memory with 2MB would be suitable for a 7200 RPM HDD.

As described before, the increase in HDD performance, as well as CPU speed and memory storage, are all very important components of overall PC performance. The RPM of HDDs available in the market are 5400, 7200, 10000, and 15000 RPM. Among them, the 10000 and 15000 RPM HDD are not typically used in the Desktop PC market, due to their relatively high prices.

Now, we would like to analyze the result of a performance test to evaluate which RPM is more effective between the 5400 RPM and 7200 RPM.

Based on test result, we can analogize below conclusion:
Based on the results of the WinBench 99 test, the system with 1.3 GHz CPU has only a 6% performance improvement when compared to the system with a 0.5 GHz CPU with the same HDD (Test A). On the contrary, the performance improvement effect of the system with a 7200 RPM HDD (Test C) reaches to 34% when compared to a system with a 5400 RPM on the same CPU. This means that upgrading HDD can be more effective for power users who use software that utilizes extensive Data input/output, to improve the performance of the PC. In addition, considering that the difference of CPU price is greater than the difference of HDD price depending on the performance, the importance is much greater when looking at the comparison in cost effectiveness terms.

In the case of the super low price PC, installing a 5400 RPM HDD is more effective, as it's necessary to minimize the cost of every component. But in case of the medium-high price PC, a 7200 RPM HDD can be an effective selection, as the effective improvement of system performance is important rather than low price.

7200 RPM Hard Drives cannot be considered absolutely necessary for all users. In some cases, it can result in potential problems such as a decrease of reliability, and increase in noise and heat generation as the price of Hard Drives increase. In spite of these potential problems, the 7200 RPM HDD will remain an excellent solution for the PC as a strategy to improve overall system performance, in a cost effective manner.