Error: Alert! Previous attempts at booting this system have failed at checkpoint [size].

Always include exact PC model and version of Windows in your posts.

You can try this:

1. Power on and press F2 to open BIOS setup
2. Copy down all current settings
3. Power off, unplug
4. Press/hold power button for ~15 sec
5. Open case and remove motherboard battery
6. Press/hold power button for ~30 sec
7. Reinstall old video card
8. Reseat RAM modules in their slots
9. Reinstall the battery (might be good time for a new one, 3-volt CR2032 lithium ion battery)
10. Close case and see if it boots now

EDITED

My computer is dell dimension 4300s with windows xp sp3.

Thank you for the advice, regrettably it doesn't seem to work. I can't enter the bios setup because the error happens in about three seconds after pressing the power button. Taking out the motherboard battery seemed like a good idea, however has seemingly no effect. Nothing else i tried worked either.

This problem may be happening because, this computer cannot use a video card with more than 64mb. Because i forgot and put in an 128mb it  now thinks it is over its limit, even though i have already put the old card back in.

Do you still get the same checkpoint [size] error message?

Did you follow all the steps I listed, including press/hold power button for ~30 sec after removing the battery, and reseating RAM modules?

The 4300s has 4 diagnostic LEDs on the back panel. What color are the 4 LEDs when it won't boot?  If not all green, look for the error code in the manual.

I still get the same error, and i did carefully follow all the steps. The diagnostic lights are

A B - orange

C D - green

The manual says this, Definition "Memory failed to be sized or enabled" Corrective Action "Reseat the memory modules"

But as i had already tried reseating the ram doesn't work. Probably because the failing memory is on a nonexistent video card.

Swapping the ram module from slot one fixed the problem. Thank you so much!

Glad it's fixed!

Did you replace that module with another one, or just remove it?

This system uses SDRAM which works best when installed as matched pairs. So keep that in mind, if you decide to buy memory to replace that one...

I just swapped the two modules  with each other. Before the problem with the video card I had been in the process of modernizing my computer, so this ram is fairly new.

Now try the new video card again.

Although i didn't feel brave enough I put the new video card in, and it actually worked! I guess the ram must have caused the problem right from the start. One of my ram is probably bad but, the whole computer is working right now. I had already packed that video card away and was gonna resell it, Thanks alot for your help.

Glad the new video card works.

Check in BIOS setup to see how much RAM is recognized. If less than the amount physically installed, that module probably is bad and should be replaced.

If BIOS sees the full (correct) amount of RAM, check in Windows to make sure it recognizes the same amount of RAM installed.

Both the BIOS and windows detect the full amount of ram. I have also used memory intensive programs that probably wouldn't work well with just one module.