Do you use doliwamp ?
If yes, by installing doliwamp 3.4.2, you should get a php 5.3. You should not lose your old data but i am not sure, do a backup before.
Yes, I’m using doliwamp. On my test server, after upgrading doliwamp, I lost all my corrected translations (not critical) and there were some troubles with invoices (i mean PDF view), I don’t remember exactly what happened. Maybe, with ver. 3.4.2 it will be okay, I’ll try.
Again, thanks for help. Updating was smooth and without any errors. Just after updating replaced new language folder with the old one, where I made corrections for my language. I think, topic can be closed.