When you booted at 270mhz, you did adjust the memory timings before booting didn't you (i.e. you know about memory timings, yes?)? If not, leaving the memory timings on auto can mean that the RAM will not be able to boot at the desired frequency. What happened when you booted at that frequency was the RAM couldn't cope (through either the timings, or the fact that the RAM is faulty). It forced a reset, but I believe the looping is caused by Windows being corrupted when this all occured. I question though, what BIOS are you running? You need to be running 310 or later (march 10th 2005 BIOS or later) to run TCCD RAM.
Reset the CMOS first - see your manual for this. It's a little jumper that needs to be placed in a certain position and then replaced back to the default position. It is near the bottom right of the board (a red jumper).
I assume that you have a USB keyboard, this being the reason you cannot select an option. You need to go into BIOS > Integrated Peripherals (I think) and turn on USB keyboard and USB mouse support. Then, pop in your Windows CD and go into the Recovery console by pressing R at the main screen. You will need to then select which windows installation you require - usually '1' > 'ENTER'. Then it will ask for an administrator password. If you have never been asked before to set an administrator password, just press enter, or if you have set it, type it here (this is not your main logon password if you have one, this is specifically for the hidden account entitled 'Administrator'. Once in, type 'chkdsk /p /r' without the quotation marks. Let this run and try to boot up normally again.
What an eejiot!
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ive got a serial adaptor thing which i had with an old board i had and im using it for my MO display 
