|"-When I start up the PC without any of the memory sticks in I get a constant beeping sound"|
That's what it's supposed to do. That confirms that the board & CPU are good & that no RAM is present.
"-The PC will start up with one or both of the memory sticks in without any beeping"
That's what it's supposed to do. That confirms that the board & CPU are good & that the RAM is being detected.
"-When I try and put the graphics card in there is no beeping but also there is no display on the monitor"
No beeping means the card is inserted properly. No display would *appear* to indicate that the card is bad, possibly the monitor. You've mentioned that the card is an 8600GTS. Are you connecting the 6-pin PCIe plug to the card? It won't work without it.
"-The HDD light doesn't flicker on start up but just stays a constant yellow colour"
You don't need the HDD connected to troubleshoot this problem. Unplug it...both the data & power cables.
"I have removed my graphics card in plugged the monitor into the mobo but on first try i got a white and grey flashing screen"
Try another monitor.
BTW, you finally got around to listing your system specs but you never posted your PSU info. Just stating that it's 500W or 550W doesn't mean sh!t. There are 500W PSUs that sell for $15 & others that sell for $100 or more. We need to know the make/model of both PSUs, plus the amperage specs for the +3.3v, +5v & +12v rails.