Build the most powerful Desktop PC as possible using only hardware from the 1990s.
Here are some suggestions on how to build a powerful desktop computer that solely relies on hardware from the 90's:

1. CPU - Look for an AMD 80386 or Intel 8088 processor, which were popular in the late 1980s and early 1990s. These processors have low clock speeds but are capable of running multiple tasks at once due to their large instruction set. You may also want to upgrade your RAM memory if you decide to use the system with more than one application open at a time.

2. GPU - If you're looking for speed and power, look for an Nvidia GeForce 256 Ti or ATI Radeon HD 4870 graphics card. These cards offer high-end features such as advanced 3D rendering capabilities and support for multiple monitor configurations. However, be prepared to pay a hefty premium for these components.

3. Hard Drive - Use a hard drive from the 1990s, such as a Western Digital My Book External Hard Drive. These drives had small storage capacities back then, but they offered fast data transfer rates and were reliable. Today, modern solid state drives (SSDs) can provide faster performance, but older hard drives still work fine for basic home use.

4. Power Supply - Choose a compatible power supply unit that has enough capacity to meet your needs. Avoid buying a power supply with outdated specifications, as it might not provide the necessary stability and reliability needed for this type of machine.

5. Chips - Don't waste your money on newer chips that will just end up being outdated shortly after purchase. Instead, focus on finding chips that match the processing power and other hardware components you choose. Look for chips that have been thoroughly tested for compatibility and stability.

6. Monitors - If you plan to use multiple monitors, make sure to buy displays that are compatible with the motherboard and graphics card you select. Older displays may not have the required connectors or display options.

Overall, building a classic desktop PC is not meant to be an easy process, but it can be rewarding if you're motivated by retro computing nostalgia. Be patient and research each component carefully before making any purchases. Good luck!