Disk full / Can't save any changes

I’m having a huge problem in my RB1000 RouterOS v4.9
It reports “disk full” and, If I change any config, when I restart the router all changes are lost.
I tried to uninstall some unused packages (calea, hotspot, etc), but it does not erase them (maybe becouse it can not save any changes!).
This Router has an old usermanager with a corrupted database that consumed all free space. I tried to rebuild or clear de DB, but always receive the same message:

[admin@Nucleo] > tool user-manager database rebuild 
Can take a while. Console may not respond while in progress. Rebuild user-manager database? [y/N]: 
y
Rebuilding user-manager database
failed to acquire DB: failed to start exclusive transaction: database or disk is full
[admin@Nucleo] > tool user-manager database clear   
Dangerous! Reset whole user-manager database? [y/N]: 
y
Resetting user-manager database
Failed to reset user-manager database
failed to acquire DB: failed to start exclusive transaction: database or disk is full

I have already deleted all files in /files. Is there any way to make some free space??

Thanks

I know that this is not the most interesting post to read, but my problem is becoming worst every day.
I have to reboot my rb1000 and when it restarted I lost all my “/ip firewall nat” configuration.
Luckily I made an export previous to the reboot, so I can recover it, but I don’t know what to expect in the next reboot!
How can I make some free space so as to uninstall user-manager??

Try a Netinstall to overwrite the entire hard drive, then apply your configuration export.

Thanks fewi. I’ll try a netinstall tonight and see how it comes.