Update?
When Windows has just started, quickly run Task Manager, and for 6 processes whose description field contains "Symantec" set:
- Priority to "Low".
- Affinity to only one core (if your processor is multicore).
And then among "svchost.exe" tind the one who gobbled ~10 000 K of RAM. Also lowerise its priority and restrict affinity.
Note that affinity should be the same for all processes. This means you give away one core, but your profit is the other cores are not occupied by Symantec.
After ~2-3 minutes the extra Symantes crocess appears. It tries to block your computer and all running programs for 5-15 minutes. You can repeat the above mentioned procedure, but the effect will not acceptable. I downloaded Sysinternals Suite and run theirs Process Explorer. With ProcessExplorer I suspend 'SescLU.exe'.
After those steps the comuter resurrects!
BTW, if you know how to automate those steps, please tell me.