the OP never once told the full story
what works good and not.
XP runs? surely it can, 0.4% 2016 run XP world wide and way less now 2018, due to virus magnet status.
do not run XP , and the fan is not XP job.
BIOS runs the fans.
if the PC runs at 56C or so and the fans slow that is normal
The bios only speeds up facts at start,
the slows them and monitors CPU heat and GPU heat
if they rise too high the fans spin up.
this is how all PC run
my fancy desktop has 600rpm fans right now, due to cool running CPU. 4 pin fans can do that magic.
The reason for the fast spin up is easy to learn turned on fresh.
the PC ASSUMES the chip are hot.
say PC parked in a trunk at 120F
the you go indoors and turn it on
so to be safe, it runs them fast (like at BIOS machine code instruction 1 or first. it spins them up then watches CPU temps live. this can take a few seconds to do a scan, see a TREND
if the trend show low, temps, it then uses a PWM fan table in the BIOS, and set the fan speed off that hard coded table)
now say PC was hot turned on then it slows only if fast fans speeds can lower the CPU temp
then rule 2 and 3 on BIOS CPU temps
if bios does not like say 80C it can turn itself off.
if failing to do that, say fan is dead, learn that ALL CPUs from P4 up
can turn them selves off they HALT.
ALL AMD and intel CPU do that.
and did you really clean it
is the RAD clean.?