I have my configuration with 1 MB of ram and 80 GB HARD disk.....
Is it possible to install linux only on hard disk and there is no use of ram.................

Computers use RAM as they can only work on data that is loaded to RAM. So with 1MB of RAM you need to find a linux distro that's installer will fit into it and later can run on such a small amount of RAM.

RAM in computers is a very similar to a table in real life and there is a rule - you can only do stuff on the table and nowhere else. So in order to do something you have to put neccessary stuff onto the table and if there is already something there, you first have to lift it off the table (swapping) and then you have enough room to put new stuff onto the table. Then there is a possibility that table is still too small for the task and you get out of memory error. As you get bigger table then you can do more work. You do not have to lift stuff off the table anymore to accommodate your new stuff so everything is faster (no swapping).

Will you please share the kind of system you have ??