Do you mean Registry Editor's 'Data' field in the right window is blank? Try narrowing the columns in the right window. You may find the I386 path leads to your optical disk drive, i.e. the one Windows was originally installed from.
If it's indeed blank, then you can either:
- Edit the Data entry, inputting the correct path to your optical disk drive, or
- Copy the I386 folder to your hard drive, then do the same as above, with the correct path pointing to its location