1. Connect ur phone to PC in MASS STORAGE mode or insert the mini sd into card reader.
2. Goto ur memory card root, u should be able to find PRIVATE folder, if not make sure u SHOW HIDDEN files in folder options of ur pc.
3. Find the folder named 10207114.
4. If u want to completely delete all the themes installed in the memory card, Delete all the CONTENTS inside the IMPORT folder
5. If u want to delete only 1 theme , open the .skn file with notepad, it will show the theme name , if u want to delete the particular theme , delete only the theme folder u wish to delete.
6. Do not delete the IMPORT OR PRIVATE folder!
addt'l steps for INNOV8...
2.1 Besides PRIVATE, you also need to open RESOURCE.
3.1 Open SKINS folder. CONTENTS would look exactly the same as in the IMPORT folder. Files will have extensions *.mbm & *.mif
4.1 Delete accordingly, following steps 4-5 mentioned above. No need to open them in notepad. File and Folder names should look exactly the same as in 10207114 folder.
6.1 Do not delete the SKINS OR RESOURCE folder!
That's should do it!
---
newb smartphone/symbian/innov8 user here. so feel free to correct any mistake/s im posting.


