Compaq dc7900 not booting past RAM check

[loriswave]

Hello, i recently got a desktop Compaq dc7900 as the title says, and i have not been able to get past the very first screen the PC displays on startup.

What happens:

I power it on, its shows a black screen (top left corner: RAM check from 0 to 2048 ; bottom right corner: "HP Compaq dc7900 small form factor - F9 boot menu, F10 setup, F12 network")

1. If i do nothing: RAM check completes, nothing happens.

2. If i press any of the mentioned F keys AFTER RAM check is complete: nothing happens. 

3. If i press any of the mentioned F keys BEFORE RAM check is complete: the F key suggestions disappear and the corresponding destcription appears in its place (e.g. Boot Menu or Setup), then RAM check completes and nothing happens.

There is a solid green LED light always turned on the MoBo when the pc is powered (both when turned on and off).

CMOS battery is fresh.

Monitor, mouse and keyboard are connected and working.

I have tried the excess current method and it did not prove useful.

Thanks in advance for any help!

[WAWood]

You say this is running Vista, so that makes this at least 10 years old if not 15, and with a PC that old, this problem is nearly always a failed drive.

See the following HP Guide for more information:

https://support.hp.com/au-en/document/ish_3053911-2842957-16