well I will personally would never advice anyone not to so something.
Bios flashing can yeild some goods.
The problem with 5700LE is obvious lack of molex.
The AGP port cannot provide more juice required to run card at higher Core and RAM speeds.
Also normally clocking RAM too high wont kill your card useless unless you clock it really too high.
I am guessing you are using coolbits to overclock which is not allowing it to go over 238DDR bcoz it fails driver test. In that case before flashing you can use Powerstrip. See if it allows you to clock your card higher.
If not first try mild overclock through bios flash. Say 240DDR. And flash the card.
See if it is able to handle that.
If it cant then no problem. Normally even with high memory clocks which gives problem in windows and games, you would probably be able to boot to DOS through boot disk and flash back to original bios.
Do not forget to make backup of your original bios using nvflash.
And use NVFLASH 4.42. This is older version but works best, better than most newer versions.
You can mod the bios using NiBiTorv.
You can find it at *www.mvktech.net
Also go to
www.guru3d.com forums.
There in NVIDIA card section there is a sticky regarding bios flashing. Read it. It has some really good tips and also ways to recover badly flashed card, And make sure you have all things you need to recover from bad flash before you flash.
Usually blind flash works without problems.