I have an old Dell Dimension L866r which I flashed with BIOS version A14.
Now when I turn on the system it hangs with the full-screen Dell logo.
If I press Esc immediately after turning it on I get the POST screen and it counts up the RAM. Once the RAM test/count is complete, the system hangs.
If I press Del immediately after turning it on I get the POST screen and and the "Entering SETUP..." message. Then it hangs.
The A, B and C diagnostic lights are green. The D light is yellow.
I have tried removing the battery from the motherboard and leaving it out for a while. I also tried changing the password reset jumper. I didn't expect these to help and they didn't.
Is there any way under these circumstances to revert to the previous BIOS version or to otherwise recover from this problem?