Question : Problem: Low Standby (VSB) voltage: dangerous? cause?

What could cause a BIOS to report Standby (VSB) +5V as 3.66V? (All other voltages seem normal.)   Is it dangerous and, if so, how?  Does it indicate a bad power supply, or could the motherboard be involved, too?  The system is described below.  The low reading is with only video card installed and keyboard attached -- no drives installed yet.

Details: Except for a n intolerably noisy motherboard "OTES" fan, which sometimes required a manual push to start, my 4-year-old system was stable.  The other day I replaced the OTES fan and, while the system was apart, replaced the power supply with a new, larger one; replaced the stock CPU cooler with a Zalman; and replaced the case fan with a new one.  Everything looked good except a low 3.67V for the Standby voltage.  That low reading held both before I had drives installed and afterwards, when I booted Windows and ran the system for several hours.

I RMAd the PSU to Antec and meanwhile installed another Antec TruePower Trio 430.  Again everything looks OK except the Standby voltage, now showing in the BIOS as +3.66V.

So did I get two defective PSUs (from different sources! the first from newegg, the 2nd from ProVantage)?  Or could it be something else?

Pentium 4 XE 3.2 GHz
Abit IC7-MAX3 BIOS rev. 18
Antec Sonata
Antec TruePower Trio TP3-430
4 - 512MB Crucial DDR SDRAM cl. 3
2 - Seagate Barracuda 7200.7 SATA 160GB (on-chip SATA1, 2 and NOT RAID)
Mitsumi FD
Plextor Plexwriter Premium CD-R/RW (IDE 1 master)
Plextor PX-716SA SATA DVD+-R/RW (SATA3)
Iomega Z250ATAPI (via Serillel2 to SATA4)
ATI Radeon 9800 XT
Zalman CNPS7000B-Cu CPU cooler
Dell Ultrasharp 2001FP 20"
U.S. Robotics 5610B "Performance Pro" modem
Audigy2 ZS
Iomega Z750USB external
Seagate FreeAgent Pro 750GB triple interface external, using Firewire
Windows XP Pro SP2

Answer : Problem: Low Standby (VSB) voltage: dangerous? cause?

... as for your "Is it dangerous?" question ==> No.  A below-spec voltage ... especially if it's only on the 5vsb line ... won't harm anything.   The primary use of the 5vsb line is to retain memory data during an S3 standby state (if you use that mode); and to power the motherboard circuitry that does a "soft power on" (when you press the power switch).   The only possible consequence of a low 5vsb is that these functions may not work correctly.