I installed a L7VMM motherboard in a new case with an AMD Duron 1 GHz
chip and cpu fan, along with 128 MB of SDRAM.  I added a hard drive,
connected the monitor, mouse, keyboard, and turned the system on. The
monitor light becomes solid, the light on the motherboard comes on,
the cpu fan runs, the light on the hard drive itself comes on
temporarily.  There does not seem to be any hard drive activity
however, and nothing appears on the screen.

See the new build troubleshooting checklist at

http://www.daileyint.com/build/trouble.htm

I suggest pulling the Cpu out and then putting back in again ..making
sure to put it in firmly..

Generally ive found if nothing comes up and the computer does not give
you a beep code the cpu needs re-seating (or is faulty)

Also, check the pin settings (if any) on your hard drive. There are
still a lot of hard drives with MASTER - SLAVE - CABLE SELECT settings
that require you to to change them appropriately. Usually, on the back
of the hard drive you'll find something that looks like this:

M S C
. . .
. . .

There are other possibilities ...

fugitive-ga

PS, let us all know if you solve your problem, and how! We're curious.

This sort of things happens quite frequently. It could be caused by
several misconfigurations of hardware or bios settings. I would
suggest u get a computer expert friend to have a look. Will only take
them few minutes to sort out.

The most likely cos are:
1. (hardware) autodetected/overclocked MOBO clockrate not supported by
CPU. (nothing on screen at all)
2. (hardware) using non 400Watts power supply - harddisk wont spin-up
(nothing on screen at all)
3. (in bios) incorrectly selected AGP as primary display driver 
4. (in bios) Harddisk are not selected for automatic detection.
5. (in bios) Harddisk boot order are not set. 
6. (hardware) Harddisk master/slave mode set incorrectly.

if u can get into the bios setting menu, you can "definitly" solve
your problem by yourself. Try hitting "del" a few times after power
on. If this does not work the first time. Try remove the power cord
completely. ie: cut out power to case. (!) be careful. Wait about 5
seconds and reconnect power. This would reset the mobo and will
re-detect CPU clockrate upon next boot.

if you cannot get into the bios settings menu at all, the most likely
senarios are  (1), (2), (3) or (6).

Good Luck!

You should start by removing and reinserting all the componants
(memory, video card) including the CPU. Also make suer that the
speeker wire is correctly plugged into the motherboard, this could be
why you are mot getting a beep code.