I believe that if you overwrite data on the hard drive this cannot be retrieved at all, not even by data recovery programmes/experts.
How does the overwrite work? does your hard drive need to be full before it starts to overwrite old info? or if I delete some data today, and another bit tommorow with that overtwrite the first deleted area or another?
And if you de-frag your hard drive does that just bring all your deleted data together in one piece that then can be overwritten? I de-frag the hdd every week and scan disk, but I'm not sure what this really does.

A true overwrite is when you have data you deleted, then filled that space with new data. Defrag will move some data around causing an overwrite condition but not completely because it moved from one location to another leaving the last bit exposed. The only way to TRULY destroy your data so NO ONE can get it is to drill a hole through the drive and then throw it into a blast furnace. A determined data recovery company can retrieve data down to the 10th level of latency.

Since the HDD has magnetic particles, not all particles will take the new data and will retain the old data 1 or 0. Depending on the density of the material on the drive and its age will depend on how far down on the media a recovery specialist can go. I just had to ship off a scsi drive from my company and pay $1500 US to have the data on the drive recovered. The drive is only a $100 US drive but the data on that drive was worth a couple mil US. Thats when I asked and found out what can be done. The drive bearings seized so they had to rip the drive appart and put the platters into a jig just to get to the point where they could recover the info...He did, the entire database (20gig in size) without much of a problem.

So, if you are concerned about your data, how worried are you and to what lengths are your willing to go to? Your normal routine is good, not great, but good for the average teen hacker to not get anything.

Sorry for the long winded message...Just had to pay that bill today...

ok, I have deleted loads of data, and probably over 4years re-installed windows os (doing a smart system restore with the masted cds) at least 5times!! so, how do I know if I have done a true overwrite? and again, how does that work? does your hdd need to be full before it overwrites? your info they recovered, did you overwrite that with other data? I have read in many articles that quite simply overwritten data cannot be retrieved, by anyone, I have even read this on some data recovery companies web site. Are they wrong? My old PC only had 5MB memory so I had to delete things on a regular basis.

If you have filled up your drive 5 times, you have overwitten the first 4 times data, but not the 5th. To truly overwrite, you need to put in every cluster, sector, and block all 1's first, then all 0's second. You need to do this for every part of the drive. This will truly overwrite all information on the drive.

Some companies can not recover an overwrite of this magnitue because they didnt spend the money for a sensitive enough read head. Yes, they are wrong, data can be recovered and parts may still be readable.

Why are you so worried about overwriting?

i accidentally overwrote a file. how would i get a previous copy of this much saved file?

Obtaining a previous version of a file which has been overwritten with new contents might not be possible. However, there are a number of FreeWare data recovery utilities you could try;

http://www.recuva.com/download
http://www.pctools.com/file-recover/ <- Not FreeWare
http://www.snapfiles.com/Freeware/sy...arecovery.html

Good luck.

thats what i was worried about. ill give it a go. i know its much easier to recover deleted data then overwritten. but ive download a program and we will see where it gets me. if nothing thanks for the help anyway.

oh this is on an external hard drive. will that be a factor??? i ran Piriform Recuva and i said it found nothing afetr a 1 second search. should i be looking on the host computer also? or just the external hard drive.