How do I convert a .txt file which contains HTML code to an HTML document?

Clarifications

just change the file extension to .htm or .html

Thank you but I already tried that. It didn't work.

As rayvyn said, change the extension, but make sure that explorer is set to display extensions for known file types, otherwise it will end up as .html.txt But , just having some html code doesn't make it an html page. Is it a well formed html page? with the opening and closing tags correct. What happens when you try to open it with IE?

1. Rename it at the command line. go to run, run cmd. navigate to the file (or move it to the root of C: for a minute. Then, ren name.txt name.html.

2. Open with Word, you save as html.

Navy,
I'm afraid Brian and Rayvin are as my old boss used to say, "off by half a bubble." Please excuse me if you've never used a carpenter's level. I digress. So, take any web page... this one perhaps.. and right click on some text area, then click on "View source". Then copy the first line and copy it to your document. Be sure appears at the top of the page, and appears at the bottom. Then SAVE AS whatever you like, being sure you have selected SAVE AS TYPE = ALL. If you are the kind of guy who uses suspenders and belts at the same time, you could use quotation marks, like: "mywebpage.htm". The key is just be sure you are not saving as txt. That's what they were trying to say. Go Navy!

Yikes I skrewed up (carpenter lingo agin) Wen I said be sure it appears at the top and at the bottom I must have hit the Control and not the Shift. The sentence should read: "Be sure < H T M L >appears at the top of the page, and < / H T M L >appears at the bottom". html&/html are special reserved words so I can use the braces in an email, but you get the idea. Just don't add all those s p a c e s that I did

back when my DOS usage was a bit more, I used a command-line utility called
TXT2HTM...just creates a simple page. Don't know if it runs in a CMD.EXE
box on NT or not, might be worth a try...you can get a copy from here:
http://www.resoo.org/docs/dos/free_software/html.htm#txt2htm1

Open the text file with IE or Firefox. You can use the right click context menu on the .txt file and 'open with', or drag and drop txt file into open browser window. Then File->Save as and select 'Web Page, html only" or 'All files". With all files, you have to manually add '.htm(l)' to the name.
However, I accomplish the same thing just renaming the txt file to a .htm. They both result in the html code being rendered by the browser, for instance < a href > stuff becomes an active link, etc.
If you want to preserve the html code as text in an html document, add this one tag at the beginning of the text: <'pre'> and at the end, <'/pre'>(without the ' in then) and then just 'save as web page' or rename the file with the .html extension.
(LOL, I had a heck of a time getting my pre tags to show, they get rendered!)

An HTML file is text. You say that it "contains" html so just open it up and double check that it actually has the structure of an HTML document. There are rules. See here:
https://www.techrepublic.com/blog/webmaster/html5-creating-a-base-template/492?tag=content;siu-container

I sincerely appreciate the responses but I am so completely confused that I cannot think straight. My fault. I think I should have provided more facts.

My online bookmark storage place is going out of business. They sent me a file called export.html.txt . I opened the file. It contains, in html, my bookmarks. They said this file can be used to import the bookmarks into IE8. I went through the procedure to import the bookmarks into IE8 but it didn't work. Only a few category names (e.g., sports, weather, etc.) made it to the Favorites file in IE8 but no bookmarks carried over.

Again, any assistance here would be appreciated. Thanks.

1. Copy all the bookmarked URL into a notepad / excel / word editor.
2. Copy each URL link into the browser. The web page opens.
3. Add to faveriotes.
4. You could also save the page and drag it to the faveriotes folder, and restart the browser, The added bookmarks will appeare.

It seems strange but if it saves time and does the work, there is nothing wrong about doing it manually.

Thanks but I have thousands of bookmarks.