This is how I upgraded from ME45 to S45i (ME45 FW26 original CE20 chipset). Most elements are from yul and Safrane but I've added some steps
1. Backup contacts/agenda to Outlook with SiemensQuickSync
2. Backup Explorer maps with Data Exchage Software
3. Make full backup of phone (S/ME45Tools) so you can recover if something goes wrong
4. Remove SIM (don't know if this is necessary)
5. Flash phone with winswup S45i v04.......
6. Depending what kind of model you have S45 or ME45 take corresponding file:
for S45 http://www.o45m.ru/program/290000x050000_s.zip
for ME45 http://www.o45m.ru/program/290000x050000_m.zip
7. Take S/ME45Tools and flash this file at address: 290000 and size: 050000
8. In S/ME45Tools go to IMEI, read phone first and press UNLOCK
9. Remove battery for some seconds (don't know if this is necessary)
10. Run S45i Activator, READ PATCHES and check out which phone values are BAD (right window). Mark in left boxes those values which are BAD. Don't uncheck other marks accept unmark S45 patch (alt) and/or ME45 patch (alt) and mark S,ME45 patch (that's also described in the right window). You can also uncheck Airplane warning if you want. Press WRITE PATCHES.
11. Remove battery for some seconds (don't know if this is necessary)
12. Start and shut down phone (don't know if this is necessary)
13. Insert SIM and start phone
14. Format flexmem in phonesetting or with Data Exchange Software
15. Download and install XTND Connect from Siemens
16. In XTND Connect settings, remove all connections between fields Outlook and phone. Set right fields Outlook/phone (address to home address/last name to last name/...) and synchronise
17. Put back your bitmaps/ringtones/voicememo's/...
Voila you have a great working S45i with all your ME45 settings
WARNING: I did everything on speed 57600 instead of standard 115200
In this topic you can read where to download the software (Divane )