Unable to power on - Compaq Presario S3000NX

This is a pretty elementary question no doubt. I've replaced this computer recently, put out in garage to take apart in spare time. I've attempted to turn it on, and NOTHING happens; this was stored in clean environment for 2 mths and working last time I used it (2 mths. ago). Not sure if it's a power supply issue or what. What type of troubleshooting can I do here ? Really just want it for spare back-up computer, nothing more.

Model: Compaq Presario S3000NX

Thank you....

 

If abosultely NOTHING happens (no fans spin up, no lights come on, no beeps) then there's a very good chance that it is the power supply. Don't ask me why, but it's pretty common for computers that have been in storage for awhile to not power up when brought out of storage. 4 times out 5 it's a power supply problem. The only real way to troubleshoot this is to hook up a known good power supply and see if it boots up.

 

I have been steering towards that conclusion. There are no lights outside and after opening up case, no fans...nothing. Good to know about storage possibility. I'll grab a working power supply and see how it goes. Thanks very much.