I just finished building a new PC that POSTs and enters the BIOS normally, but it repeatedly restarts when I try to boot from Windows installation media on a USB drive. The cycle is consistent: the amber DRAM light stays on for about 10–15 seconds, followed by the red CPU light for around 3 seconds, the white GPU light for 3 seconds, and then the green Boot light with the ASUS splash screen. After roughly 3 seconds at the splash screen, the system restarts and repeats the same sequence.
The USB activity light flashes during initial startup and again when the green Boot light appears, but it shuts off immediately before the restart. Without bootable media connected, the system enters the BIOS normally and can remain there for hours. CPU temperatures appear stable at approximately 38°C. The BIOS is updated to version 3902, dated 07/13/2026.
The system consists of an ASUS ProArt X670E-CREATOR WIFI motherboard, Ryzen 9 7950X3D, ASUS TUF RTX 4090 OC, 2×48GB G.SKILL Flare X5 DDR5-5600 memory, a Samsung 990 Pro 4TB in M.2_1, Samsung 860 EVO and 870 QVO SATA drives, and a Seasonic Prime PX 1300W power supply connected through a Singularity Computers PowerBoard.
I have rebuilt the installation media, tried another USB drive and different ports, reseated the power and data connections, changed the Secure Boot setting to Other OS/ignored keys, disabled Fast Boot, tested with one memory module, tested with and without the dedicated GPU, used the BIOS boot override, cleared CMOS, and reflashed the BIOS. What else could cause the system to reboot only when attempting to start the USB installer?
3 Answers
An overheating CPU or incorrectly mounted cooler can cause immediate shutdowns during boot, so it is worth checking that the cooler’s protective film was removed and that it is mounted correctly. However, since the CPU remains around 38°C and the machine can sit in the BIOS for hours, an instant thermal shutdown seems unlikely here.
A Linux live USB could be a useful diagnostic. If Linux also fails in a similar way, that would point more toward a hardware, firmware, or USB-controller issue rather than something specific to the Windows installer. It may also help to look up the motherboard’s debug-light sequence while testing.
One useful detail to check is whether the Windows loading spinner ever appears before the restart. Knowing exactly how far the installer gets may help narrow down whether the failure happens during USB detection, bootloader initialization, or early operating-system startup.
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