Thats what happens
The no signal message we've refered to is generated by the monitor when it hasn't got a picture to display (at least most monitors these days, others just refuse to come on).
When the computer is powered up it goes through several steps to check the machine out before you get to see the graphics card message (followed by the bios string and drive search etc.)
If any one of the pre-checks fail you usually get a beep code, indicating the fault, e.g. 1 long beep meaning no memory, 8 beeps meaning no video card detected (these are if you have an AMI bios) etc. If it just seems to lock then, in my experience, it's usually down to a component being detected correctly but failing when asked to do something (as it would then require more power.) This manifests itself as system lock ups where all the components seem to be working but nothing happens.
Do you hear anything (beep code wise) when trying to power up?
Another thing worth trying is running:
http://www.memtest86.com/as it tends to identify dodgy memory and power supplies. Be aware it does take a while to run as its a very thorough test.