My compaq presario do not start, instead it make two sounds like a beep and then nothing, what coulds happen. it is the mother board or is the hard disk?

ah a tower

you check the power source output
this can be replaced as a whole unit

at power up should be a beep
if the mother board is good it will start up its default
before loading from the hard drive

make sure the dust is removed from all the internals
clean all the contacts
the fans and cards and main board

It could be anything but probably a power supply error.
Power it down, wait 1/4 hour and power it up. Listen for the error beeps and that will tell you where the fault area lies. Error codes are listed in your manual for the mother board or indeed with the manufacturers web site.
If there are no beeps, replace the power supply and try again.
Hope that helps.

For some reason the disk is not being registered in the BIOS. Bent pins can cause this problem. Is the disk firmly seated?
Did it quit working "suddenly" and you replaced the disk? If so, it sounds like the disk controller circuit on the mother board has gone bad.
Put the disk in a desk top and see if you can read it. (Takes special laptop cables or a special adapter. PC shops could test it.)
If you can see the disk contents, then for sure you have a problem on the mother board.

First remove the Ram and boot the system without it. If you hear continuous two beeps, then the problem is with the Ram, you need to replace it. If nothing happens, then your cpu or your motherboard is gone. Good luck. Thanks for using FixYa.

First of all check whether there is any CD in the Drive. If your system is configured with CD as first boot device, instead of Hard disk and there is non bootable disk in the CD tray this could happen. If you find a CD in the tray and removing it gets your computer to boot normaly, then change the first boot device to Hard disk in the BIOS. If this is not the case, check the power and IDE cable into the hard disk for any loose connection. Check the IDE cable at the hard disk end as well as the mother board side. If this also alright, you may want to check the hard disk for probable fault or corrupted operating system.

It sounds like the RAM is either not compatable or is bad. Put the old RAM back in and try again. Also the V2000 and HP DV2000 is in recall for mother board problems.

there is problem with u'r SMPS. repare it or change a new one

refurbished motherboard may have corrupted bios inside

Try to go into the bios settings and restore default settings. It could be a bad setting in you bios thats causing it. If thats not the case it could be bad ram. Are there any beep codes during this process? *Beep codes are beeps that happen when you turn on your computer and there is an error, Most mother boards use them.

Before you get too excited with buying a hard drive
Go Take a look at what the beep code means
And possibly it is as simple as reseating ram or something
http://www.bioscentral.com/beepcodes/compaqbeep.htm
Hope this helps you