It may not be possible to reflash the bios yourself. Dell is particularly anal about locking down otherwise adjustable BIOS settings, and the application to flash the bios that is available from dell support will only work if it hasn't been updated. The currently available updated bios version is 2.5.3, so if a different BIOS version appears at POST you should be able to update it...
Flashing the bios on an XPS 410, (and most other older Dells), is a matter of downloading the update
, setting it to run in compatibility mode for windows vista, and running it as an administrator. I've done it dozens of times without a hitch. The main thing to remember is run the bios flash on a freshly installed OS with no antivirus or other security software installed, and make sure there are no other running applications before you start.
However, don't do it unless the problem reappears after zeroing the HDD and reinstalling windows and
you've checked that one or both of the other symptoms are present (rcpnet.exe in task manager and/or an unchangable or missing setting for the security chip) Otherwise you're wasting your time on something that won't solve the problem.