Does anybody know how stable the 7650 is? Could a (makesis.exe) created *.sis file corrupt the os and render the phone useless, just showing the nokia logo followed by a black line(several times) before switching itself off?
Nokia 7650 is based on Symbian OS, therefore, it is considered to be stable.(Now, I used for long time without data lost) Symbian create a personal-device OS, compare to other OS manufacturer (mainly operate on PCs), which steal your time with bootups and restarts.
However every system may have week points.
There is Nokia OK logo for protection of consumers. If app/sis-file have this logo, you can trust.
Otherwise, special software developers coding error may result program code which render a Symbian based phone useless. Even in this stage, authorized service personal have 80% chance to get the important information out.
A normal application is usually not capable to make damage of any kind into the system: System is in the ROM. There should not left any major error in sis-files "alpha releases".