Only half of RAM usable

Try to test it with CPU-Z and see if your memory's even being recognized by the system like I said. It really sounds like you might just need to re-seat the sticks.

Yeah, CPU-Z can detect my 3 sticks no problem, seems my computer can't... this calls for a WTF moment. :/

Wow that is absurd. You can take a (or 2) stick out and then reboot, watch the POST beep and come up with a "system memory has changed" error and say okay and let it boot. Then turn it off and stick that other one back in to any free slot and hopefully the "memory change" error comes up again, so it'll start a-new and run it with all 3 sticks. If not it could be your motherboard or chipset driver, I'd definitely try and update them.

If that doesn't work, I'd punch your computer in the face if I were you.

IT WORKED!!! FINALLY!!! Thanks a lot, been worrying about this and haven't been using my computer much, can finally return to gaming! :)

What'd you do?

If your 430 i using an older BIOS an upgrade might help. Unfortunately, a bad BIOS upgrade could also turn your computer into a giant paperweight.

Vostro 430 - Dell - Search - All Dell.com

This may be one of those times to see if the folks on the Dell forum have any other suggestions. It's just puzzling that all apparently was OK up until a week ago. I also found the 430 specs for memory. Doesn't say anything about what slots to use if you're using an odd number of sticks.

Memory
Memory module connector 4 DIMM slots
Memory module capacity 1 GB, 2 GB, or 4 GB
Type 1066 MHz, 1333 MHz DDR3
Minimum memory 1 GB

Maximum memory 16 GB

Source

Yeah... me too. What fixed it? I was apparently typing over your repsonse.

onesixski said:

Wow that is absurd. You can take a (or 2) stick out and then reboot, watch the POST beep and come up with a "system memory has changed" error and say okay and let it boot. Then turn it off and stick that other one back in to any free slot and hopefully the "memory change" error comes up again, so it'll start a-new and run it with all 3 sticks. If not it could be your motherboard or chipset driver, I'd definitely try and update them.

If that doesn't work, I'd punch your computer in the face if I were you.

Something like that, taking out the sticks and replacing them one by one. It seems that when I was swapping out sticks I might not have installed one of them correctly or something.