Picked up an old compaq deskpro. complete, but w/o on/ off switches

you can download the mother board manual from the internet...

yes i think it is sorry to the bearer of bad news my freind have you tryed the card in a freinds news computer to rule out the chance itsa a bad card? hope this helps if it does then please give 5 thumbs up

This isn't a sure fix by any means, but...
You could try unplugging the unit from the wall socket and opening the case. Touch a metal component inside the case for a few seconds to equalize static charge between yourself and your machine.
Next, remove the battery on the motherboard, and wait 5-15 minutes before reinstalling it. What this will accomplish is to reset the computers' BIOS (Basic Input Output System) settings to the defaults for the motherboard, which may let the machine figure out what processor you installed.
If it works, your machine will boot up, and you'll get an error message telling you that there is a checksum error or simply that a BIOS setting is wrong. You'll have to read the message and press the appropriate key to get into BIOS, then reset the date and time.
I hope this helps in some small way- It's rough attempting to set up a machine if you have no visual output to let you know what's going on.
If my solution gets you up and running, please let everyone know by writing a testimonial.

What model compaq?
Have you tried HP.com ? If OEM they will have the driver. If not I use driverguide.com for drivers I can't find. mysleuth

http://search.hp.com/query.html?lang=en&search=++&qt=Intel+Solano+i815&la=en&cc=us&charset=utf-8

To upgrade from a Pentium 3 to a Pentium 4 processor, you would have to replace the motherboard. The Pentium 4 processor has more pins on it than the Pentium 3 and would not sit in a Pentium 3 motherboard.

http://www.bioscentral.com/beepcodes/compaqbeep.htm
Go to the above site contains beep codes for compaq
I believe your ram is faulty or needs removing and refitting

take the old ram chip(s) out. The speed should be the same. e.g. PC100, PC133 etc. and install your new chips

Check with your motherboard documentation.
May i know your motherboard model??

Hi,

Depending on the actual model of the old Compaq, you can enter the CMOS/BIOS setup by pressing on the a special function key or key combination during Power-On Self Test (POST), before the operating system loads. During POST, the BIOS usually displays a prompt such as:
Press F2 to enter Setup
Common keystrokes that will access the BIOS Setup are F1, F2, F10, and Del. For older Compaq computers, like the Deskpro 286 or 386, you must place the Diagnostics diskette in the A: drive, and then restart the computer.
For newer Compaqs, like the Prolinea, Deskpro XL, or Presario, while the cursor is at the top right corner of the screen during bootup, press the F10 key.

The hard drive controller can not be replaced without replacing the motherboard. Incidentally, there are old PCI sundcards that has an IDE port and can be configured to replaced defective on-board IDE port.

If your concern has not been addresses after completion of the above procedures, you may need to seek the services of a qualified professional.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.

Dimensions: 254mm = 10.0" x 218mm = 8.5 inches. This is the current size of motherboard in the Compaq.
http://stason.org/TULARC/pc/motherboards/C/COMPAQ-COMPUTER-CORPORATION-Pentium-DESKPRO-2000-P.html