Question I have an old Gateway DX4840, and I put in the motherboard from a Lenovo Thinkstation P300. (Also had to swap CPU and PSU) Now it doesn't turn on.

[Xnihilo]

As stated previously, I have a Gateway DX4840. My CPU initially was an i5 650. Graphics: ATI RADEON HD 5570. 6GB of RAM. Now, I'm looking at upgrading it for gaming, so I swapped the motherboard to the one I had in a Lenovo Thinkstation P300, which did previously have a hard drive blown. Well, put in the motherboard, PSU and CPU in smoothly, plugged everything else back in, and plug in the pc. Almost instantly, PC fans start spinning, but I don't hear the regular single beep (meaning successful power-up), and instead heard a beeping in the pattern of sirens! Any ideas? Also, not to be rude, but I really want to have this question solved by friday. (Going out of town to a large city with far more components for sale than I have here in my city, and we only go there once a month) HELP!!!
There is good news, though... Sometimes, it doesn't beep at me. Once or twice, it didn't make siren noises, but didn't give proper power on beep. Once, U saw the moniter turn on, and list my SATA ports! That is basically the only thing that gives me hope! I know my PC wants to work, it just isn't working.... YET!
Also, forgot to mention lenovo mobo specs: it has a Xeon processor, (sorry, not sure which one yet), amd had an odd 14 GB of RAM. I received it from a friend, but couldn't log into it. He took it back ti the server PC it was previously plugged into to log in there, but blew the hard drive. Possibly damaged the CPU? I don't know. And, all the fans in the PC spin, but sirens come on. Didn't do this to me before upgrading mobo. Instead, my Gateway ran well. However, I might have bent a CPU socket pin.

 

[Alabalcho]

You have to find out the original manual for the replacement motherboard, and see what these "sirens" mean. Most probably - CPU or RAM are not recognised.

Disconnect everything but CPU and RAM. Checking this page about P300, it seems it has integrated GPU. Start with single RAM module only (if supported). Once booting stable, update the BIOS (the best would be with from standa-alone USB/CD boot image).

 

[Xnihilo]

My Lenovo came from the same friend, and he gave it to me with a Quadro K600. The GPU I am using is ATI RADEON HD 5570, So I need GPU, too. Now, once or twice it started working, showed stuff like connected SATA, Ram, other stuff. Then it just turns off, moniter on power saving, more sirens. Is it my BIOS? My heatsink? My CPU? I have no clue. The ram worked fine in my other PC (6GB), so I don't see why it wouldn't work. Also, thanks for helping! I almost wondered if it would go unanswered!

 

[Xnihilo]

Also, the motherboard came from the P300, and I don't have the manual. I will try what you stated tomorrow, but in the meantime, please continue the flow of info! Thanks!

 

[Xnihilo]

So I have an old Gateway DX4840 that I want to upgrade for light gaming. I also have a Lenovo P300 given to me by a friend. It is worth noting that the P300 once blew a hard drive. Well, I took the motherboard, PSU and CPU out of the P300, and put it into the Gateway. Turn it on, moniter blank, says DVI POWER SAVING MODE, constant police sirens. The fans are all spinning. Why is this happening? I might've bent a CPU pin, but before I investigate more, I NEED HELP. Here are the specs:
Gateway before upgrades:
ATI RADEON HD 5570 1GB
INTEL CORE i5
Stock motherboard (I believe it is a Gateway manufacturer custom)
6GB RAM
350 watt PSU, Liteon
Standard Case
Windows 10 Pro (I upgraded)

Lenovo P300:
Nvidia Quadro K600
Not sure about cpu
Custom Lenovo motherboard, Lenovo stock
12 GB RAM
240 watt PSU, Liteon
Standard Case
Windows 8

Now, I don't know what the BIOS is for either, and it's hard to check when my PC doesn't turn on. However, I also researched and found that the police sirens mean CPU fail/overheat/something isn't on right. Well, it certainly isn't overheating, because as soon as I turn it on, it says, "ack yer processor is like on fire or something." The RAM I am using is the stuff from the Gateway, 6GB, and I am almost 99.99 percent sure the RAM is seated properly, and all sockets are DDR3. So please guys, I'm open to anything.

 

[Xnihilo]

Alright, so I found it uses Ami Bios. Sirens means something with the CPU. Any suggestions?

 

[Alabalcho]

Start with clearing BIOS settings, there should be a jumper somewhere to do that (or remove the coin battery, wait an hour or two).

Is this the same CPU that motherboard came with, or you transplanted another one? This could also indicate issues with the power supply, although I don't believe this is the case with SFF setup.