The PC after is switched on runs till the black screen with thermometer after BIOS report shows for a short time, than restarts itself and runs normally.
Can not be this strange behaviour motived with same bad activity during OS loading? But the PC run without problems until the firewall change.
OS is Windows XP home, SP2, the last firewall was Sunbelt, payed version.
Thank you for comments.
Try disabling D+ and see if that changes things or not. Go to Defense + → Advanced → Defense + settings → tick “Permanently disable the Defense + (Requires a system restart)” → Ok and Apply your way out and reboot. Does the same thing happen?
Are you sure Sunbelt was properly uninstalled? I don’t have an uninstaller tool for Sunbelt but can give you the following general approach to see if traces of Sunbelt are still around.
We are gonna take a look to see if there are some old drivers of your previously uninstalled security programs are still around. Go to Device Manager → View → show hidden devices → now look under Non Plug and Play drivers → when you see a driver that belongs to your previous security programs click right → uninstall —> reboot your computer.
When the problem persists make sure there are no auto starts from your previous security programs. Download Autoruns and run it.
This program finds about all auto starts in Windows. This tool can therefore seriously damage Windows when not handled properly. After starting go to Options and choose to hide Windows and Microsoft entries, to include empty locations and then push F5 to refresh.
Now check all entries to see if there are references to your previous security program. When you find them untick them. After unticking reboot your computer and see what happens.
I found two notices: “Sunbelt HIPS driver” and “SbFw”. Both went out. The reboot of PC waits to night but I think, that this two relicts are guilty. (But the uninstal was done correct, using the propriet steps.)
Many thanks for help. 
Let us know how things go.
So, sometimes OS starts 2x, with Defense+ off or not. During the use of the Autorun utility, we switched off “rdpclip” (do not know, why it run) and Windows autoupdate. We will see, what will be in the future. Thanks for patiency.