The green light flashing is a diagnostic LED light, telling you there is a power failure.
More specifically a bad Power Supply.
Weak voltage power rail.
The Power Supply used in a Compaq Presario SR1010Z desktop computer, is a 300 Watt unit, and is an ATX form factor.
[ATX form factor for a Power Supply, denotes the size of the Power Supply case, and the shape.
It is approximately 6 inches Long, 6 inches Wide, and 3-1/2 inches Tall.
The ATX form factor for a Power Supply is used in over 90 percent of the personal computers out there, and is as readily available as the air we breathe]
Usually, HP uses one of three generic Power Supply manufacturers.
All are low quality Power Supply manufacturers.
This is HP Support, and the main menu page for the Compaq Presario SR1010Z desktop computer,http://h10025.www1.hp.com/ewfrf/wc/product?product=1146324&lc=en&cc=us&dlc=en&submit.y=7&submit.x=6&lang=en&cc=us
If you click on Manuals, then on Upgrading and Servicing Guide on the following page, there are instructions on how to open your computer case.
This is instructions on how to replace a Power Supply, from HP Support,http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01356113&cc=us&lc=en&dlc=en&product=3548196
(It's for a Pavilion a6230n desktop computer, but after you open the computer case of your Compaq Presario SR1010Z, the instructions are the same)
What Power Supply would I recommend?
There are 100's to chose from.
This is but one example,http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3276575&CatId=1078
1) Maximum wattage is rated at 450 Watts.
A computer ONLY uses the power it needs, and NO more.
Wouldn't matter if you had a 10,000 Watt power supply, (No such thing. An exaggeration), if your computer only needs 100 Watts, it would only use 100 Watts.
(Surfing the internet typically uses 100 watts)
2) Has all the power cables you'll need, and more. Tie up the power cables you do not need. (Use plastic ties, Not wire, or bread wrapper ties)
3) 24 Amperes (24A) on the 12 volt power rail.
4) 135mm cooling fan.
The cooling fan on the Power Supply you have now is 80mm.
A larger fan turns slower. Produces as much air as a smaller fan, (Or more), but makes less noise.
Less wear on the fan's bearings also.
5) Is an ATX form factor Power Supply.
6) It's 80 percent efficient, compared to the 60 percent efficient Power Supply you have now.
(That is, if it was working)