My "hp pavilion a220n" won't power on. ... I was

http://www.manualguru.com/hp/pavilion-a220n-desktop-pc-us-can/quick-start-guide

Check your mainboard for power connectors.

The main one is a 20Pin some-times 24pin.
The next area to check is a 4Pin CPU power connector, which is loacted around the CPU socket. Top left of the board.

Take care!
damnor01

HP Pavilion 9694C memory upgrade specification, Pavilion 9694C maximum memory, memory speed, and memory upgrade options. Upgrade memory on HP Pavilion 9694C upto a maximum of 256 MB
PC100/133 SDRAM DIMMs, with maximum 128MB per slot in 2 memory slots. The HP Pavilion 9694C takes the PC100/133 SDRAM DIMMs Memory Type.

Hope that helps.

If your disk space is low on the Hard Disk drive, delete or move some files off. You can replace the hard disk for 30-50 dollars with a larger one. If it is low on memory (RAM) you can add more up to the system limit from several sources.
Thanks

Check all wires for loose connections--- if the memory was wrong or something, it would still attempt to boot but stop during the POST and start to beep

One of larger wattage won't hurt at all. If you put one in of lower wattage you might find yourself without enough power.

According to the link below you can do the upgrade. If is not working, make sure you have the memory seated correctly, then mix and match the memory and switch slots to find the problem memory. It may be incompatible with either the motherboard or the other memory sticks, or just a bad stick.

http://www.insidemylaptop.com/upgrading-memory-hp-pavilion-zv5000-series-laptops/all-comments/

yes it can be upgrade for 4GB for genuine HP memory. because hp exclusively use hp memory. all Hp pcs uses genuine hp memory.

This can be due to several things and usually its the last change you made. When you try to turn it on, do you see the fan moving on the power suppy (rear of computer) If this fan is not on I would suspect the powersupply. A power supply can give you a lighton the front and not supply enough power to start the computer.
Next i would remove the cover of the computer (usually two or three phillips screws on the back) and physically inspect all the cables and add-in cards and make sure they are all fully in thier sockets.
If you have added memory recently, a wrong voltage or speed could cause a non-booting system.
check these things and post again if this doesnt help .
These are only a couple steps , but the first steps you should take after trying to boot into safe mode unsuccessfully .
There will be more to check if this does not work, so dont rate untill we solve the issue..

HP Beep codes are listed here: http://h10025.www1.hp.com/ewfrf/wc/document?docname=bph07107&cc=us&lc=en&dlc=en&product=329076&dlc=en&lang=en None of them matches your description, so listen again and see if the pattern matches any described by HP. Have you tried the monitor on another computer? Did you connect to the onboard graphics connector? Look for any loose components, especially memory.