the final update

(maybe!)

right, after lots of good advice (tnx guys) i did (another) reformat, and then re-instal of c:. all was ok, used th pc a bit - but not anythign to heavy, eg no copying big files etc.
then , because the d: drive had gone funny last night i decided a reformat of that was in order
so did that, then restart and i cant get into widnwos, nothing new there!
so disk check in the recovery console, and here som,e results

Checking file system on D:
Volume label is Storage.
Cleaning up minor inconsistencies on the drive.
Cleaning up 1 unused index entries from index $SII of file 0x9.
Cleaning up 1 unused index entries from index $SDH of file 0x9.
Cleaning up 1 unused security descriptors.
CHKDSK is verifying file data (stage 4 of 5)...
File data verification completed.
CHKDSK is verifying free space (stage 5 of 5)...
Free space verification is complete.
Adding 27492954 bad clusters to the Bad Clusters File.
Correcting errors in the Volume Bitmap.
Windows has made corrections to the file system.

208354985 KB total disk space.
253496 KB in 95 files.
64 KB in 31 indexes.
109971816 KB in bad sectors.
72473 KB in use by the system.
65536 KB occupied by the log file.
98057136 KB available on disk.

4096 bytes in each allocation unit.
52088746 total allocation units on disk.
24514284 allocation units available on disk.

this was first time i had done a reformat and disk check straight after instal (shud hav done it b4!)
but i think i found th rout of all my problems - bad sectors

the reason i hadnt come to this condclusion before is i had never done a scandisk on a blank d drive,,,,, or i had run it thru windows and then you cant see results.
anyway im petty sure this is why when putting large files on d: it messes up - because they are going into the bad areas....

next question is, now that the system knows they are bad [a whole 100GB has been marked as bad! and i can only use half (100gb) of my "storgae" D drive now!] will it keep them bad and just not use them? i guess when i have reformatted before it did not know they were bad, hence the reocurring error - it kept trying to use them each tie i reformatted. so will the drive be ok to use now? or will more secotrs keep going bad? eg it will deterioate..........
does anyone know if its possible to fix a bad sector - thus making my WD HD useable again, and a 250 gb not 150 gb (i heard of a program called HD regenerator that can actaull fix a HD? how is software capable of doing this!!?)

Sounds like you have a HD going bad, I would try a run with Spin Rite 6 at level 5. If you are not familiar with Spin Rite look here grc.com