Best thing of all, there isn't a single option to update the BIOS... no flashing / updating utilities / tools... Nothing in the BIOS.

I did download a few updated ROMs from ASUS' site. Found an old hard drive, will try to connect that one to see if it will boot up (to try and rule out hard drive malfunction).

That's actually pretty normal, there usually isn't anything in the BIOS itself that will allow you to update it. It's usually done outside the BIOS by downloading a bootable disk image of some type that will flash the BIOS for you.

How come? :) The last 3-4 BIOS updates I did had an update utility inside the BIOS. I can't find anything bootable for this motherboard, ASUS M2V-TVM (it is from 2007 I think), just simple ROMs.

EDIT: There is a tool for updating, downloaded that one too, but it requires Windows... And the HDD is empty, grrrrr. I'll try to connect an old HDD right now.

Updating BIOS is not like updating your operating system or other software. You are not just copying over files, you are erasing and replacing the BIOS code, hence why it is normally done completely outside of the BIOS itself. Some newer machines have the ability to update within the BIOS (though that is really just a download, the installation of the new BIOS actually takes place during a reboot) or even through a Windows executable. In the case of the ROMs you have downloaded, I would have to guess that there is some external utility that your motherboard would normally use to apply that ROM, either in the form of a bootable disk or Windows executable. A little Googling and I did come up with this:
http://www.ehow.com/how_4885286_update-asus-bios.html
The AFUDOS.exe that article mentions is available many places online.

These motherboards do a flash from either the BIOS pages (press DEL during POST to get into the BIOS) or a boot floppy. Depending on how the POST sequence is set up, you may not get prompted to press DEL; just press it blindly if this is the case. (You can also flash the BIOS from within Windows, but if Windows won't install, that's cold comfort.)

They are known to be troublesome with Windows 7, and ASUS does not even support Windows 7 on these motherboards. You may have to use the Vista drivers when you get far enough to allow drivers to be installed.

The next thing I would try is clearing CMOS. I would also make sure that your Windows 7 disk is not defective. A big scratch will cause this kind of problem too.

You may also have to remove some memory, if there is more than 2GB installed, just long enough to get the installer to run. This was definitely a problem with these boards under Vista.

Thanks for the effort. I burned several ROMs to a CD, started the flashing utility, but it doesn't recognize any of them. I also tried renaming them, to match them to the asking file, still no luck.

EDIT: Baaaaaah! Didn't want to check that as answered. :(
The PCs don't have floppy drives though.
Already had removed the other RAM sticks, both PCs are now on a single 2GB DDR2 stick.
The Windows 7 discs are fine, 3 of them, actually, OEM copies, still unused. How do I clear the CMOS? By removing the battery for some time?

You can usually get around that by making a bootable CD or flash drive instead.

The flashing utility doesn't recognize the official ASUS roms for the motherboard, so what's the point in burning them again... :(

Gonna try that old hard drive now.

When solved, repost the question and have the person who solved it post the solution. I don't think you can undo it so I will edit that post to disregard the answer as the solution.

It's a multi-step procedure on this motherboard. See page 1-18 of the manual, at http://dlcdnet.asus.com/pub/ASUS/mb/socketAM2/M2V-TVM/e2710_m2v-tvm.pdf

Clearing CMOS will get rid of any weird settings that may be interfering with installation, but it will also reset the clock, so you have to go back into BIOS after clearing, and set the clock and anything else that needs setting.

I still fear this install is going to be a battle. You have motherboards that haven't been made since 2007, using chipsets that were made in 2005. ASUS doesn't support Windows 7 on that board, and VIA didn't make Windows 7 drivers for the chipset (they say Windows 7 has native support for the chipset).

You may need to make a slipstream disk with the motherboard drivers on it.

How to

I use a USB floppy on XP but finally just made some slipstreams as the old XP install disks didn't have the drivers for the new MB / SATA hardware

This may work out, but you'll have to use the Vista drivers. (There are no Windows 7 drivers for that hardware.)

BIOS should now be at the latest possible version, as it doesn't recognize the new versions. Done with that, but still no changes to the system.

Connected the old hard drive, but can't boot from it (not even in safe mode, it restarts before the Starting Windows screen appears), even though it has XP installed.

Gonna try to clear the CMOS now.

Guys, thank you for all the replies so far. :)

Sounds like that may be the only option.
If the BIOS did update you might want to reinstall Win 7 as Win 7 has a huge amount of drivers on the install disk. If it was just the BIOS needing an update, Win 7 might install correctly now.

Do be patient with the Win 7 install as it takes some time and often seems to be locked up or rebooting for no reason.

Edit: IIRC, the last Win 7 install I did took around 1 1/2 hrs on a slower, older machine. I thought it was locked up but the HD light was still flickering. Finally finished the install successfully.