All for Compatibility.

The goals for building this retro PC are:
- To run Windows 9x games, especially those requiring a certain level of CPU and GPU performance that make them difficult to emulate smoothly
- To use affordable, reliable, and easily obtainable parts
- To keep the system slim and compact
Games that are extremely old and speed-sensitive can be run using emulators like DOSBox or 86Box. Additionally, it would be ideal if this system could also serve as a platform for running Windows Longhorn betas (which require a 2003-2005 era DirectX 9 graphics card).

TL;DR – Here is the final configuration I chose:
- CPU: Intel Pentium E5300
- Motherboard: ASUS P5KPL-AM SE
- RAM: 2GB DDR2 800 Single Channel
- Graphics Card: ATI Radeon X300 SE
- Sound Card: Creative Sound Blaster PCI CT5807
- HDD: Western Digital WD5000AAKX 500GB SATA mechanical HDD
- Optical Drive: Samsung TS-H652 DVD-RW
- Operating System: Windows 98 SE/XP Dual-Boot

About the selection of each component:
- The most important factor is the motherboard chipset. After watching PhilsComputerLab’s LGA775 video and stumbling upon some forum posts about installing Windows 98 on LGA775 platforms, I became convinced that running Windows 98 on a PCIe chipset was feasible. Based on shared community experiences and my own previous retro builds, I decided on an Intel chipset. The most common and readily available motherboards use the G31 or G41 chipsets, and their paired ICH7 southbridge still offers native IDE support. I ultimately chose the G31 chipset.
- Regarding the motherboard itself. The board needs to have both PCIe and PCI slots to accommodate a Windows 98-compatible graphics card and sound card. I also want to use ethernet to connect to my NAS. This means the onboard LAN had to be a Realtek RTL8111D or earlier, or I need an extra PCI slot. Combined with my goal for a compact build, I settled on the mATX-sized ASUS P5KPL-AM SE.
- For the CPU, I chose an affordable and cool-running 45nm dual-core. The Pentium E5300 happened to be the same model from my first computer in 2010, so I went with it.
- Some claim that single-channel RAM performs slightly better than dual-channel under Windows 98. My own testing showed that installing 4GB of RAM would disable the 3D functionality of the graphics card, even when using Rudolph Loew's LIMITMEM patch. I opted for a single 2GB stick of DDR2 800MHz.
- The ATI R300 series has PCIe versions that are compatible with Windows 98 and are generally more stable than the GeForce 6000/7000 series. I chose a half-height Radeon X300 SE. For Windows 98, even this low-end card is overkill in terms of performance.
- The only half-height sound cards I found compatible with Windows 9x were the Sound Blaster PCI CT5806/CT5807/CT5808. The CT5807 also supports connecting to HD Audio front panel headers via an adapter cable. The Sound Blaster Live! has no half-height version, and the half-height Audigy variants (SB0410 and SB0570) are not compatible with Windows 9x. Half-height cards with other chips like YMF744, CMI8738 or ES1938 are nowhere to be found.
- The WD5000AAKX hard drive is a classic and very reliable.
- An IDE optical drive supports CD Audio output. Most SATA optical drives have removed the 4-pin analog audio output.

Installing Windows 98 on such a configuration inevitably requires some hacking. I modified the installation disc using patcher9x, integrated the ESDI_506.PDR patch and Intel chipset drivers, replaced fdisk and format with modified ones, and extracted defrag and scandisk from a Windows Me installation disc. I added limitmem.sys to config.sys to limit the usable memory to 256MB for Windows 98. Installing the drivers was a bit tricky, but once everything was set up, only the mostly useless ATK0110 sensor lacked a driver—a compromise I can live with. Interestingly, installing the VXD driver for the Sound Blaster PCI on this machine caused a "fatal exception 0E" BSOD, while the WDM driver installed correctly. To my surprise, the WDM driver also provides Sound Blaster 16 emulation and General MIDI support within Windows' MS-DOS mode.

Getting the sound card working in DOS was a long-standing headache. The official Creative drivers would load and General MIDI worked, but sound effects were unavailable. I eventually settled on using SBEMU, which, ironically, allowed me to avoid AudioPCI's horrible FM synthesis emulation altogether.

Here are some photos of the build:

I'm super satisfied with this compact build and it will be my only retro rig in next years. Thanks to all these amazing works and my friend who nicely designed and 3D-printed half-height brackets for the video and sound card!