M7160N Pentium D 820 (2.80 GHz) with slow Ethernet chip.
The CPU and GPU and other fans are BIOS controled
the PSU fan is hard wired (cooper) to the inside of the PSU 12vdc power rail.
the PSU is not programable at all wiki how ATX PSUs work
it has only power on pin (and OKAY out)
one bit in , 1 bit out status. no fan controls period there.
one could at great pain, buy upgraded PSU that runs the fan only when overheated, Im sure someone makes this but would
take me all day to find (sorry not doing that) or I could design one.
OTHER FANS, just to be complete....on topic fans.
Why is that a problem?, why not let your MOBO decide this.?
The mobo has a job here, not to let key parts
overheat.
The MOBO bios runs the fan. (it's rules, unlike laptops, dual modes)
What WINDOWS (unstated OS by you)?
if really curious ask HP. may be there is fix for this.
if at all.
if running XP(why?) , learn that sleep and hibernate will fail
learn that those 2 features to work right all drivers for all things inside PC must have working current drivers.
XP is now dead for 4 + years, do not run XP the Virus magnet.
best is to avoid that, running XP or VISTA , unless PAIN is fun.
best is to upgrade, buy PC with w7 on it and works prefect.
a win there, no? 2007 or newer PC, avoid all others.
but sorry the PSU fan still is not programmable. yet.
carbon dated, has office 2003, new so is 15 years old?
users guide 2003 to 5. ;yah old.
https://h30434.www3.hp.com/
the 1millionth post lacking OP stating OS
windows what? must we guess, and lie to you?> that it?
its a system and we cant guess what you have new or after 15 years what has changed, from new.. sorry.