unmountble boot volume

Hi mate, could you post full BSOD and also your system specs please???
What make/model is your HDD??? Go to manufacturers web site and download testing utilities and test your HDD to check if you have some bad sectors...
Also test your RAM memory also with memtest you can download here: www.memtest.org
Hope this will help you mate...

Hey there, its a pentium 4, 2600MHz fujitsu siemens.. not sure of the HDD spec.. the os wont even boot so I imagine I need to reload windows xp, boy what a mess!!:

Hi mate, you can see what type of HDD is yours in BIOS... You just need to press 'del' or 'F1' or like that [will be shown in startup screen'... You can see in BIOS what make/model is your HDD and then you can test your HDD for possible bad sectors...
Also maybe it is faulty RAM memory, you can test it too with Memtest...
It is better to be sure what is the problem because if it is HDD or RAM problem, even if you reinstall XP you will still receive BSODs ...