What is the processor fan speed for Dell Vostro A860?

Bad inverter or possibly a bad video card or M/B.

Yes, go into the bios and change the setting and give it a try.

Have you tried blowing out the fans with a can of compressed air?

The computer is overheating, and is shutting itself down, to prevent heat-related damage.
Turn it off.
Disconnect the AC power.
Remove the battery.
Purchase a can of compressed-air, and give your computer a "blow-job", shooting air everywhere inside your computer, to try to remove a layer of dust, which is acting like an insulating blanket.
Re-insert the battery.
Restart the computer -- listen to hear that the fan(s) inside the computer are running, i.e., the fans have not "seized", due to being plugged with dust.
Reconnect the AC power.

It should be normal, make sure you don't block air from bottom the laptop or any sides because that is where fan sucking the air to cool off the core. If that does overheating then it should be shut down by self because it already built in temp sensor for overheating protect.

Its stuck on finding a bootable device. your PC has a virus or HDD is gone bad (unlikely). Try putting in the OS disk n boot for it.

Need to reinstall windows, insert your windows disk and boot from it.
If that does not work buy/get a new AC adapter and/or battery.
if that gets you no where open the case area around the fan use a can of compressed air n blow it all out.

This could be a sign that your laptop is overheating. If you touch the laptop while it is running & you find it too hot, make sure that the fan is running properly & that the air ways are not blocked.
You can blow compressed air into the cooling vents of the fan. If you notice clouds of dust coming out, then it might be a good idea to disassemble the laptop, clean the fan & air ways, & reassemble it back. If the fan has failed & is no longer running, it might need to be replaced.

If none of this solves the problem, or is not the case, then you might have a bad motherboard.

Hi,
you can download all the driver for your Dell vostro A860 notebook from here follow this link to download the drivers,
http://www.getpcmemory.com/drivers/dell-vostro-a860-download-dell-vostro-a860-notebook-windows-xp-drivers/

this will solve your laptop driver problem
Thank you for using Fixya.

Regards
Manish

Try one of my Tips & Tricks which i had published

http://www.fixya.com/support/r4681055-speed_tune_up_windows_vista

I hope it might help your Notebook run faster.