Now I noticed that you state that you have 4 drives/partitions, and you can only make 2 active.
Exactly how many physical disk you have?
Each physical disk have how many partition(s)? (List out all)
For your information, each physical disk can only have 1 partition as active mode of which of this is a primary partition, this is used for disk booting purpose.
If you have 2 primary partitions on a single physical disk, you can only set either 1 as active mode which your OS reside and you want to boot from there.

Now that clear out some confusion. Not sure how bad it's but you can try set the 2 partitions that you already backup-ed to other attribute so you can set the other 2 to primary so you can do backups, note that I haven had this problem before nor did I tried this so this suggestion is on your own risk.

Could be a bad sector or file corruption. Did you try "chkdsk /r" on all your partitions?

Could be a bad sector or file corruption. Did you try "chkdsk /r" on all your partitions?

While we may eventually see such numbers as HDD sizes goes up, you shouldn't be seeing it for the Samsung F3 1TB. If the "chkdsk /r" test does both read and write, it should complete the scan of the entire 1TB in about six hours. I think your HDD is damaged. If you agree, it would be best to backup what you can, securely delete your personal data and then RMA it. RMAed HDDs are almost never returned to you, as they'll replace it with another HDD.

Every hard disk has its own issue, I dealt with Seagate (mine), Western Digital (both mine and office) and Samsung (mine and friend's experience), Hitachi (office).
Seagate 500GB Barracuda (first few release) has firmware issue (firmware from Thailand batch); severe firmware issue that caused the corruption of hard disk's BIOS and hard disk is not detectable, until I found problem on the web, my hard disk already being sent for RMA and they return me a new one, lost 300GB of data.
Western Digital, my 1TB Green right now has some "RAW Read Data" and "Current Pending Sector Count", both this attributes however still under acceptable condition but who knows it might affect your data? Though the data is not so important but this could happen to anyone, so watch your SMART!!
Samsung, yeah, their support over other hardware is still poor although it's on the market for quite sometimes, this make them revise their marketing strategy. HD103SJ has some issue with some Gigabyte mainboard that my friend's had; only detected 32MB after format... (=.+") Samsung HD204UI has firmware issue with AHCI NCQ features that might cause data corruption under certain case, flash the firmware helps but since I use IDE legacy on my SATA so currently doesn't face this issue yet.
Hitachi, reviewed to have the best durability but still dies on some my office HP PC, although data lost is minimal.
So there's no reliable brand to start with, just depends on your luck and always aware and backup from time to time if your data is critical.

i had a 2.5" samsung hdd before and it spoiled fast.
i m getting a 1 TB 2.5" soon..is there any brand better than samsung but with reasonable price?

what issue is it? my frenz 1tb samsung f3 also died after 6mth of usage, all of sudden cannot boot-up, put into docking station also cannot be powered-up, i suspect the culprit was faulty pcb; anyhow, already get his replacement unit within 1-wk

i got few units of f4, so far so gud, but they mainly for storage purpose, so no intensive read/write activities

Check your Event Viewer. It will be logged there. Try checking every entry from the applicable time range, there shouldn't be too many entries.

Bestest bang-for-the-ringgit is Samsung 1TB HD103SJ @RM169. Good performance and runs cool.
You do the maths ya?

For those who still able to get cheap price for Samsung 1TB F3, better do so, you won't believe how much they have been raised.

RM305 for Samsung 1TB F3

i wonder why my old IDE HDD can't be detect , i already buy the sata converter but my pc stil can't defect my old ide HDD =(