Just to reiterate, I don't know for sure the XPS 8900 has TPM and I don't see any Win 10 drivers for it listed on the XPS 8900 support page...
Have you been using TPM and/or Bitlocker on your hard drive for security?
Is all your data backed on external media? You might lose stuff if you disable TPM (may be called "Intel Platform Trust Technology", or "PTT" in BIOS, if it's there). So do whatever you can to get it to boot and then back everything up on external media before looking to disable TPM in BIOS.
Before you reseat the RAM, power off, unplug and press/hold power button for ~15 sec before opening the case. Read the Service Manual for instructions to remove/install RAM.
Forum Member since 2004
I am not a Dell employee