at least a dozen ThinkPads, and ThinkCentres, you have a major problem. The splash screen is generated by the BIOS and if there is nothing displayed, back to statement one.
Depending on the age you might try replacing the BIOS battery. It may help, but don't count on it as the battery only saves settings, not bootability. A dead battery will still allow boot but the clock will be wrong. I'm assuming you KNOW the monitor is working.
Here is the specific model http://www-307.ibm.com/pc/support/site.wss/quickPath.do?quickPathEntry=8183DGU
On ThinkCentres, hitting the Enter key will bring up the BIOS access screen. Power up, give the machine about 5 seconds, no more, and start pressing Enter, tap, tap, tap. Your first choice will be Enter setup, Choose temporary boot Device, Choose Network boot. If there is no response or still no picture on the screen, you probably have a "couple bucks" door stop. The ThinkCentre has integrated video and that MAY be the problem.
Hope you didn't pay much.