All updates (including software) are availablehere
In the Archive section.
Just in case, here are the direct links to the 2003SE ROM:
For BT versionhere
For the version with WiFihere
After the firmware on 2003SE still need to update the usb-driver - and it updates it directly in the ROM, takehere
It is also recommended to update the Bluetooth stack from the E800BT to the 5th version, as well as separately install the third-party software that is in the first 2003 Windows in ROM. All this can be found at the first link.