OK, since you're using NX 7.5 I assume that you are saving your symbols in the Reuse Library. When you create a symbol you have the option to save the symbol either inside the current part file or in a reuse library folder. Out of the box, unless you've either defined some of your own symbol folders or have downloaded some standard symbols from the reuse library the system will only offer you the option to save the symbol in the part file. However, if you have any additional folders defined, then they will also be available for storing your symbols.
Now you're already learned that storing a symbol in a part file only makes that symbol available while you're working in that part file and not with any other part file. So you need to save the symbols in an actual reuse library folder. To do that, go to...
Customer Defaults -> Gateway -> Reuse Library -> Symbol Library
...and in the box titled 'Symbol Libraris' enter the desired name for the library and the full path to the top level folder. If you're not using Teamcenter then enter the path to a native Windows folder in the upper box. If you're using Teamcenter enter the infodba path as defined in Teamcenter in the lower box. The format should look something like...
My Symbols|D:\User_files\symbols
...where the entry before the '|' is the desired name of the library as it will appear under the Reuse Library tab on the Resource Bar or in the Folder View section of the Custom Symbol dialog. Now you can have subfolders in this top level folder and they can go as deep as you need them to be.
Anyway, once you've set-up your folders when you create a Custom Symbol, rather then selecting the folder named 'Part part Symbols', select one of the other and save your symbol there. Note that since you will in actually be saving a specially formatted NX part file into this folder (that's what a Custome Symbol actually is, a special type of NX Part file) you will be asked to supply TWO names, one which will be the actual SYMBOL name and the other for what you wish to name the part file (they can be same name or different, that's up to you).
Now that you're saving the newly created symbols in an actual Reuse Library folder, you will be able to access them for use in any part file that you wish.
BTW, if you're running native Windows and you would like to access a set of system provided Symbols which are part of the NX install, include the following entry in the top entry box on the Customer Default page described above...
PMI Symbols|<where NX is installed>\UGII\symbol\PMI_Symbols
...making sure that you use the path name for the NX install location.
Anyway, I hope this helps solve you dilemma as to "Where dis my symbols go?"
John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
To an Engineer, the glass is twice as big as it needs to be.