I.have a HP presario this PC haven't been used like a year ago now I started to used it I get that signal,can anyone give me an idea how can I start the PC or what or how can I get it fix

Excuse me, but I don't really understand the problem. Isn't it a good thing that your monitor is receiving a VGA signal? (Presumably your monitor is telling you that it is receiving a VGA signal.)

Perhaps, as your system is booting up, your monitor reports that it is receiving a VGA signal (probably a good thing) and then fails to finish booting for some other reason?

Please describe exactly what happens as you try to turn it on.

Perhaps the internal bios battery failed and the PC reverted to defaults. If so replace the battery and set the bios to use the correct graphics. If the PC has both onboard as well as an add on card, it may be sending the signal where you do not expext.

Bios should auto detect but good thing to check.
Also your monitor support 2 connection types maybe VGA and DVI inputs possibly a HDMI input
Make sure u have proper cable and configuration on monitor (sometimes u need to specify the input) there should be a uto detect button on monitor as well