Well i reseated the memory sticks just in case. I also checked the event log for the latest episode of freezes. Loads of errors the main ones were as follows....
"disk error" \device hard disk 1\ D (controller error, there were around 20 of these from 3 sessions)
"ntfs" file system structure on disk is corrupt & unusable. Run chkdsk on volume F:\ (only one of these errors)
"atapi" parity error on device\ide\port 2 (3 or 4 of these)
the one that worries me most is the ntfs error....could it be damaged files or a problem with the integrity of the data drive.
the log also recommended running chkdsk on the F drive. Do i run that from within windows (the run command ?) or some other way.
all opinions gratefuuly received.