Compaq Armada E500 Rom error

I/O error could be the hard drive or the driver on the mainboard
take out the hard drive and see if you still get the I/O error
if you dont get the I/O error than its the Hard Drive
hope it will help

Try resetting the BIOS to the default settings and reboot

A PXE-61 error message is most likely a faulty hard disk.
Try reseating the hard drive first and if you still get this error message again then you need to replace the hard disk.
To boot up with the CD you maybe able to press the F12 function key when you power up the laptop, this will bring up the a menu option to select an alternate boot device. If this option is not available then go into the BIOS configuration and change the bootup order and make the CD as the first boot device and the hard disk as the second device. You can can it back later.

if you are sure there is one long beep and one short beep then it is a hardware issue most probably motherboard issue or else video card issue. get it inspected by a technician there.

sound slike theres a fault with a cd dvd drive or that it's disconnected, possibly the driver is corrupt

Did you change the '1st boot' drive to the optical drive?
If you haven't, you need to enter the BIOS setup and change from C: to whatever your optical drive is named and then change it back once the operating system is installed on the C: drive.  

Is you cd-rom drive shot - are you trying to boot up your computer through an xp or windows cd? If it is, it's not going to recognize and boot up. You'd be best getting a new drive - look around for someone with a Compaq Evo 800cp. They have the same exact cd-rom drive. Here are your compatible cd-rom devices:
TEAC DW-224E-A
or a Compaq DVD-ROM DRN-8080B
otherwise try a HP SD-C2612. I have these three drives. They all work really well.

Not always the Hard drive, boot into the bios setup utility and de-select network bootfrom the boot options. If it tries to network boot first you will always get that failure.

remove the memory chip and try

Make sure the boot order did not change in the BIOS.