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Okay, thanks for valuable suggestion.
I took my Samsung Netbook to Lamington road. A repair guy took out its hard drive and asked me to buy case, cable for it from street outside. Got that for 125₹ and then hard disk was simply slided into that case & fixed for 50₹ and then formatted it and still using it as external HDD
I roamed to entire market but no shop has enclosure,they suggested to visit lajpat nagar, so i ordered it online at 5x rate of yours. 
So basically from ur comment, formatting is must to use it, have u taken any backup before such procedure?
I wouldn't recommend using a wear out hdd for data storage especially if the data is important. But if you are a dare devil and still want to proceed then get a 2.5 hdd enclosure, look for it local market as online ones are costly. Once you fixed the hdd in enclosure just plug it and copy the important data(if not already done) to your ssd or other media, once you are done with that open your disk management utility and delete all partitions(can also be done by diskpart utility easily) once you deleted the partitions create one massive partition with NTFS file system(to store large files can also use exFAT but NTFS works amazingly in windows for recovery and all) now format it(tick quick format if you can't leave your laptop running for hours) and done you get your own external HDD.
PS: I am using eira 2.5 usb 2.0 case as i got it for 150 from a retail shop nearby and my disk is formatted in two partition using GPT partition table and are formatted with ext4, using at as a router disk
I just read your hdd is running Ubuntu so ideally the file system should be ext4 and ext4 is not natively supported in windows. there are two options to backup data, first boot from the ubuntu itself and copy data. Secondly use 3rd party tools in windows like diskinternals linux reader and ext2read to copy data. More power to you.
There is no need to format your hdd. Windows will recognize it as an external hdd and you can see all files and folders exactly the way you saw when it was internal hdd. But because its bootable, and if you have the first bootable device set as usb hdd in the boot order in your bios, it may boot from it if you have it connected at boot time.
it has os in it and it is bootable so how will it work.
Ek storage medium ke tarah hi kaam karega. Koi dikkat waali baat hi nai. 🙂🙂🙂
Edit: agar aap Linux daale hain toh file system ext4 etc hi honge. Toh wo windows read nai karega. Toh Ext2read use karna padega. Koi dikkat wali baat nai hai.
