First, you should fix the CPU Fan problem. IF it really has failed, you need it fixed SOON before it gets to be a bigger problem. First step: just open the case and observe whether the CPU cooling fan is turning at reasonable speed. If not, it probably has failed and should be replaced immediately. If it is turning, try this: shut down, then unplug and reconnect that fan where it plugs into the mobo. Do this a couple of times, then start up again. Does the fan turn? Does the error message still come up? The unplug / reconnect operation may scrub the pins clean - both fan power supply and fan speed signal pins - so that it works OK again. But if not, you should replace the fan.
Now, you say the HDD is shown in BIOS. Is your optical drive (CD or DVD) also detected? Check where you have set up your Boot Priority Sequence. The usual way is optical drive first, then the particular HDD you normally boot from, and then no other choices. Make sure the right HDD is specified (if you have more than one). If you changed anything here, don't forget to SAVE and Reboot.
If that does not solve your problem, check these two items:
1. Is your optical drive empty? If it contains a non-bootable disk the machine will try to boot from it and fail, but the error message will not be exactly what you said.
2. Did you have a second HDD in your machine earlier when the OS was installed, and then remove it recently? If so, you will need either to re-install the drive you removed or do a REPAIR Install from your OS's Install CD to restore some files that were on the (now-missing) second drive unit.