Windows XP Pro - How/Why would a folder/subfolders suddenly become read only?

[Muse]

One of the hard drives in my WinXP Pro desktop has a top level folder named Data. Today I suddenly found that everything in this folder and under it in subfolders is read only! I changed it back (which took Windows a while). I am flummoxed. How did/could this happen?

 

[fr]

Did you try running CHKDSK?

 

[Muse]

Did you try running CHKDSK?

No, but I will! Thanks.

Edit: Don't know if this is a good idea, but I'm running the Disk Check in Windows XP, having checked the boxes for Automatic fixing and Attempt recovery of bad sectors. It's a Seagate 200GB HD, maybe would have been a better idea to run Seatools, or even CHKDSK /R in a command window. Is that the same as what I'm doing?

Edit2: Evidently CHKDSK /R would just do the same thing... Uh, but maybe Seatools would be the better idea?

The drive does show a CAUTION when I run crystaldiskinfo, reallocated sectors being the problematic entry.