MY hp 6730 b the Pro fan some time to fast speed .and som tym its help for few second befor this very slow and not working.

it could be a damaged coil in the motor motor speeds are on the windings on the motor.

change the fan ASAP, since the zooming noise and the slow performance will affect even the processor and you might end up replacing the processor as well if it persists. So get the fan ASAP and problem will be solved.

old post.
odd symptoms.
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)
get that?
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.
ok?

and did you really clean it
is the RAD clean.?

http://www.pcdied.com/overheated.html

Yes, you need to replace the fan motor. Here is a link to the part you need.

The fans are essential to the cooling of the processors and everything else in there, if they are running fast then usually that means your processor is overworked. I'd go for a fresh operating system if you can.
The fans should come on really fast when its first turned on, then slow down after a few minutes.

replace the capacitor.

pull motor ,check for burned wires onfan and bak of fan speed switch,fan could be the problem un hook fan and conect directley to 12 volts and see if varibles exsist,if so replace fan motor/look for a fan resister if all the other things check out

hai
In ur laptop right click the C: and click properties ,then select disk cleanup follow the instruction and delete the unwanted files like temp files, cookies ,etc and ur system will increase its speed

You normally have 3 screws - idle speed - slow running and fast running.
First take care as if it runs faster than idle speed that chain will be whipping around also.

Second you have to determine what is the problem. Is it faulty at low speeds or high speeds ? or won't it idle.
If it has turn stops fitted to the screws you only have a small adjustments either way.

If it won't idle, try turning in the idle screw a half turn - until the chain just starts to move slowly.
If its dying at slow speeds, get is going and slow turn the slow screw out until it starts to run a bit rough then turn it back in to the point where its running smoothly.

Bad fast speed can be caused by simple things such as a blocked muffler ( insects too - I had one blocked off by a mudnest wasp) - otherwise get it running at full and adjust the fast screw as per the slow one - out till its rough then back in slowly until its smooth.

Suggest before all this tho that you get it running with the cover off the carby and then give it a good squirt of carby cleaner first - it may just clear out any 'poop' thats there.

(Have faith even tho I have a Poulan with a carb that refuses to run on anything but carby cleaner. I have pulled it apart a few times and renewed all the perishable bits buts its a real pig)

of course..is that phone line, by chance a high speed internet connection?