Dell Inspiron 6400 runs for 2 hours or so then throws up a DIMM A fault

SOURCE: Dell memory Dimm B errors, 2 gig memory upgrade

I've put my original 256mg card in DIMM A and my 1gig card in DIMM B and have had no additional problems. So I'm just living with 1.25gig of memory...

SOURCE: Dell laptop Latitude c 810 BIOS revision A12

you got the wrong type of memory installed open the memory bay and remove move it from socket 1

SOURCE: No sound in my Dell Inspiron 6400 laptop

If the issue is no sound after reinstallation of Windows, then your issue is most likely a driver issue. Many items in the system will function with native windows drivers but the audio on a I6400 is not one of them. Installation of drivers in the correct order is critical to Dell portables functioning correctly. Correct driver order is:

Notebook System Software.
Chipset Utility
Video Driver
Audio Driver
Modem Driver
Network Driver
Wireless Driver
Touchpad Driver
Quickset Utility

All other applications and drivers (MS Office, Printer driver etc)

This system is also equipped with Media Direct capability. For Media Direct to function, the system's HDD must be prepared using the Media Direct installation CD, then WIndows installed, then the Media Direct application. If you have no plans to use media direct, this can be skipped (Most people do)

SOURCE: Micro phone not working in my DELL Inspiron 6400

Though I have inserted a microphone plug at Del 6400 socket still my laptop microphone system is not working , please help

SOURCE: how toturn on wireless in dell inspiron 6400

you should have a key on keyboard in lower left corner by windows key that says"FN" then hit "F2" that should do it, if that is not the case then there should be a switch along the edge of machine