Hi anxy99,
This could be a common problem on PCs and laptops. Often after Updates are downloaded, usually via the Tuesday
"push" updates from Microsoft, sometimes your
BIOS will simply lose track of it's
Boot Preference, in other words the Boot Drive device (C: Drive) in Windows. Try accessing your
BIOS via
F1, F2, DEL, F9, or F10 key on power up of your laptop. There will usually be a logo screen (
splash screen) with the laptop maker's logo; i.e. Dell, Acer, Gateway, HP, Toshiba, etc. In the
BIOS, go to Boot Preferences and select your Hard Drive, usually the brand of the hard drive is referenced such as
WDC (Western Digital) or
ST(Seagate), or other in the Model number as well as the capacity such as 500GB, or 1TB, or 3TB, etc. Make sure the hard drive with your Windows on it (the one you put in the external enclosure to test) it is the
FIRST device on the list. Other devices might read
"CD/DVD Internal Drive", "USB device", or
"PXE Network Adapter", etc. Many laptops have a
F12 or F9 key or some-such function key to access
"BOOT PREFERENCES" directly without having to access the
BIOS. These will change it temporarily, and if you select your Hard Drive in the temp
"BOOT PREFERENCES" menu, it will work for 1 time--but not after that unless it's set correctly in the
BIOS. This method will tell you right away if it's simply a boot preference or boot order issue.

Once you know that and your hard drive boots up into Windows ok, you can then figure out how to access your laptop's
BIOS and fix the Boot Preference permanently. Once you get your hard drive to boot up into Windows properly, you've then identified your problem, and it's pretty easy to fix.
You can download the Owner's Manual from the website of the laptop maker (Dell, Acer, HP) and that will give you details on how to access the BIOS for your particular laptop model.
If this still doesn't work, post back your result, and we'll advise you further.
Best of luck,
<<<BIGBEARJEDI>>>