You should not use a vacuum inside a computer at all, it can cause many problems.
You should use canned compressed air to blow the dust away. You may have a working vacuum nearby to catch the airborn dust.
Did you unplug the whires going from the motherboard to the front pannel?
The case power switch is one of those. It must be reconnected on the right connector. Your motherboard manual have graphics showing you where all those whires must connect.
If you don't have a printed version, you can download them as PDF documents from the Acer web site.
Here is a direct link to download the user manual:
http://global-download.acer.com/GDFiles/Document/User%20Manual/ACERDT_UG_EN.zip?acerid=633645847884347295&Step1=Desktop&Step2=Aspire&Step3=Aspire%20M1201&OS=V10&LC=en&BC=Acer&SC=PA_4
Is the power cord of the computer realy connected to the wall outlet? Or to a power bar connected to the wall AND switched ON?
Make sure that the main power cable from the PSU is correctly connected to the motherboard. ALL the way in and locked in place. You should not be able to put it in the wrong way.
If you removed the RAM, make sure they are correctly inserted in and locked in place.
I hope that you did NOT remove the CPU.
If you did, make double sure you put it back in the correct orientation and that it's securely locked in the socket. Check if it have any bent pin.
If there are bent pins or it's surface contact model that have been placed the wrong way, it may be destroyed and may need to be replaced.
Spread a SMALL amount of thermal compound and put the heatsink back in place. Connect the CPU fan.
Make sure that all your cards are back in the proper slots and inserted all the way in. They don't need to be inserted in exactly the same slots as they where previously.
Tripple check that your video card is properly installed and that any auxiliary power connector needed is actualy connected in.
Make sure that the monitor cable is correctly connected to the video card's outlet.
Make sure that this cable is also correctly connected to the monitor.
Make sure that the monitor's power cord is actualy plugged in and that the monitor is actualy switched on.
Some of the check points may look sily or obvious, but you never know...
Electro, April 2011
