No display on monitor, compatibility issue?

Question

Iron

Upd2: The problem was solved by itself, in an incomprehensible way (disconnected the PSU wires, installed another video card, it worked, returned the "native" video card - it also works).
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Was:
Jetway M26GT3-SVP (Am2 socket)
Athlon 64 3000+
ddr2 PQ1 1 gb
Palit GTX 550 Ti
I don't remember the brand (it broke down and I was asked for something do something).
1 hard drive and 1 dvd-rv (both Sat)
Together with the replacement of the PSU, I decided to upgrade a little and it became like this:
Jetway M26GT3-SVP (Am2 socket)
Athlon 64 x2 5000+ Brisbane G2 (ADO5000IAA5DO)
2 slats ddr2 PQ1 1 gb ( the number of chips is different, but the markings are almost identical)
Palit GTX 550 Ti
PSU FSP ATX-500PNR (combined load of 12v 408 W, 18 A), new
1 hard drive and 1 dvd-rv (both Sat)
When I assembled everything, it immediately started working. Windows loaded, which was installed, I ran a stress test in AIDA for 10 minutes. Everything is good.
The next morning I turn it on - there is no image on the screen, although all the fans are spinning, the hard drive access light blinks.
Additional power is connected to the video card. Power to the processor (two 4-pin) is also connected.
If you remove the GTX 550 Ti and connect the monitor to the built-in video - there is an image, everything works.
Capacitors on mat. whole board.
The contacts on the memory strips are cleaned, the system unit is clean, without dust, the wires are neatly laid.
Ps There is no overclocking, everything is by default.
Upd: The video card works on another computer. In Furmark in idle time 34 degrees, under load it rises to 79. That is. with cooling everything is in order and the card itself is working.

Answer 1

See the BIOS settings for the main video...

Answer 2

Disable the system hard drive and enter the BIOS. If everything worked out, i.e. the image is present on the external video card, then the problem is in the video drivers. Try booting in protected mode and reinstalling them. If there is no kin, then deal with the BIOS settings. If you had not connected the power to the card, the beeper would start beeping.