ya dude you can save it as a .map file and reopen it you have to just save it as a if i remember correctly a .rmf file

ur not suposed to open it as a .map file just a .rmf the map file is to compile it. what oporating system do you have because with window 7 you dont even see the .map file if you open hammer 3.4 go to file, open. so i dont understand what you mean. id you double click the .map file it wont even open in hammer.

ok here is how to compile a map

1. download a ZHLT for this link- http://bmmaps.weebly.com/uploads/1/0/1/0/1010915/zhlt.rar
2. once done downloading extract files (can use winrar or 7zip).
3. now right click mapname.bat and hit edit.
4. it should open in a notpad if so you see mapname and other stuff all the mapname's you have to change the name of the map you want to compile.
5. now you have to make sure that all the paths are right(this is where it gets tricky because not everyone has the same location of the steam place).
6. now save and exit and double click the mapname.bat and it should compile if it does nto just pm me.

I would recommend you to use Batch Compiler if you can. I dont know how well this runs on W7, but i prefer this program to the "manual" option of the above comment.