Check the documentation on your motherboard and see if there is a CMOS reset jumper you can use or a CMOS battery to take out.

Try doing a hard reset: plug the AC adapter into the laptop/wall, take out the battery, hold down power for 15 seconds. If that doesn't work, you might've caused some serious internal damage such as cracking the motherboard in half or, though unlikely, maybe even knocking the CPU out of the socket.

Could be a lot wrong with the laptop, but the slowness and video issues I have seen as a result of improperly seated or malfunctioning RAM. The power issues could just be an underlying battery issue which shouldn't be causing video issues or slowness. But then again, it could also be a bad logic board doing some funky stuff. With this many issues, I would take it to somewhere with apple certified tech's who can run diagnostics on the laptop to narrow the issue down. That's the first thing that I do with MBP's with this many problems as it's hard to tell what is causing what.

Make sure you check your laptop's BIOS to see if you are on the right boot device first of all. I believe the way to do this on a Compaq is: turn it on, mash ESC key until a blue menu comes up, hit F10 for Set up, then check Boot Priority. If it is on your HDD, then reboot to mini xp and run the command "bootrec /scanos" through command prompt to see if your computer recognizes a bootable OS. If these both check out then post back with results.

If the laptop is on windows 8, 8.1, or 10, hold down the shift button while you click the restart button from the start menu and let go of the shift key after you see the scrolling wheel saying "Please wait...." Then you will have some options on a blue menu, the bottom one should say "Advanced options" which you should click on. Then click on reset and follow the on screen prompts. If you aren't on Windows 8 or above, try downloading JV16 power tools and running their "Decrapifier" which deletes non-factory default apps and programs. After that, you can just delete your pictures/music/videos and run CCleaner's wipe free disk space option if you are worried about someone recovering your files.

You say that it turns off AFTER displaying the logo. Does this mean that the logo disappears and Windows starts loading? If it does, then it is probably just some OS corruption, so you might just try restoring/refreshing depending on which OS you're on or rolling back registry hives (if you had restore points set up). You'll probably need a windows repair disc to boot from if this is the case.

This is a pretty common one that I've seen for macbooks. A long, and I do mean longgggggg, white screen sit time is indicative of a bad logic board. The first HDD probably wasn't even bad but the logic board just wasn't reading it. To confirm this, you might take the HDD itself to a repair shop and most people will be glad to plug it in to a docking station or sata-usb cable to test it for you.

Have you tried using ethernet to connect yet? If it does, then just use that connection to re-download drivers for any "Unknown Devices" in device manager. If your ethernet does not work, then you will need to do one of the following: 1. Buy a USB Network Adapter (which normally start around $35 for something decent) 2. If you already have the Windows 10 bits on your computer, go back to 10 and download drivers. 3. Use a different computer to download driver installers onto some kind of transmission media (USB/CD/DVD) or, 4. Take it to a repair shop that has these tools

First of all, are both the lights on the ethernet port lit up? If they are then it's most likely a cable or driver problem. Try the ethernet cable in another computer and if it works, try reinstalling drivers. To do so, hold down the windows key + R and type in "devmgmt.msc" in the box that appears. Expand the "Network Adapters" section and right click on your "Ethernet Controller" driver and hit uninstall. Don't check the delete checkbox that may appear on the first prompt, but just keep hitting ok until the dialog boxes stop. Then restart your computer and see if the ethernet is working.

Yep, I agree with mayer. To prevent these issues in the future, make sure that you are properly ejecting your drives, shutting down your laptop/computer properly, and keeping the external in a place where it won't get banged around. If the externals are still having problems after formatting/proper usage, you might want to contact Western Digital for their warranty, which I believe is 2-3 years per HDD.