Virtual Machines don't start after converting from physical

Did you disable stop/physical hardware related services prior starting the conversion?
Disable other services which you think not suitable to be run in VM as well
Or at the VM console you can try to go into safe mode and disable those services

No, I didn't.  I (probably mistakenly) thought it was a "simple" enough server that I didn't dumb it down before copying it.  I'm thinking about installing a copy of Acronis with Universal Restore, and just recover a backup image into the virtual machine that way.   I'm still learning a bunch about the physical-to-virtual process, as you can tell.

That's fine and yes you can import disk image as well using vmware converter, you should be able to stop/disable in the vmware converter itself, look closely you will have the option to do so
Cheers!

On the hardware properties make sure the boot hard drisk is listed as scs(0:0) I've seen it change it to 0:1 and cause this error.  If you server converted as a buslogic controller change it to an LSI parallel controller and see if resolves the issue

Ahh....SOMEONE ELSE GOT THIS TOO! I just did a conversion and it workd flawlessly. I did a second conversion and this very thing happened. Thanks for the info "Paul"...I will look more closely at the scsi association, as well as the buslogic properties.

~coolsport00

You should also use an iso of floppy or CD with an application to check the active boot disk.  If the second disk is set as active you may need to change this as well

The server I virtualized is a little Dell PowerEdge pizza-box server, with a Celeron CPU and 256MB of memory.  It's disk system is all IDE. There is no SCSI controller. The video is from the motherboard, and shows up as an ATI Rage with 8mb of video memory.

Although it is a Dell, I installed Windows 2003 server standard on it with as no Dell addons, other than what was required (device-manager-wise) to get a clean view in Device Manager.

One odd symptom seems relevant: In vSphere, when I reset this vm, I see the vmware logo, and I  quickly press the F2 key, but it never has let me into the BIOS.

I can easily enough re-run the Converter process, but there's not much to turn off that makes this server unique.

Try this:

Download a trial copy of Symantec Backup Exec System Recovery Server and image the server.  then use the vConverter to convert the image to a VM.

f you're using Dell OEM Windows license you will have an issue, it will not let you register Windows since the OEM license is looking for Dell hardware.  You may need to perform a Windows repair using a Volume License Disk and license.

I ran the "Configure Machine" task in the vCenterConverter Standalone product, and now I'm able to get into the BIOS with the F2 key.  I ran through the BIOS options, and they looked OK and jibe with what the physical server is.  

Now, I get a hardware vmware logo, a hardware BIOS post, a booting mode, and then the blinking cursor on a black field.

A second VM on the same setup is supposed to virtualize my Netware 5.1 server.  There, I'd like to start the VM running an ISO image of Portlock Storage Manager.  I've uploaded the ISO that I used to burn the CD, and the CD boots other PCs.  I've pointed to that ISO as the CD in the settings file. But the VM keeps going straight to trying to boot from the Ethernet card and look for a PXI image, which isn't available on the LAN at this time.

I tried downloading one of the appliances from the VM Marketplace, so that I could confirm that some VM, any VM, would run on the host.  It did run.

I'm unclear why my VMs won't boot my ISO images.  They're bootable in Hyper-V.