PC Stuc in power save

I have adell dimension 5150 its a few years old, however we hadnt used it in a fec months, but set it up today, wored lie a dream, then i went to do stuff and came bac and I am stuc in power save...I have removed the Cell Battery as advised on other posts, but nothing works.
There is a strange noise comes out from it also, I have got rid of all the dust also.

Please can someone advise