|So the problem seems not to be at this entry, but there are several other registry keys, you have to check.|
I assume, you've already checked, whether there is an additional entry in the Startup on "Start / Prorams / Startup" !!!
Ok, so lets start:
1. open regedit
2. press CTRL+F to search registry entries.
3. search for "runonce" without the quotation marks
4. we only need the results found at the left side in the regedit program
5. if found an entry at the left side, directly above you'll see a key named run
6. click on the run entry at the left side and check for "default" entry at the right windows side
7. this should always set to "value not set". If not, click on it and press the delete key.
8. press the F3 key to search the next entry (keep in mind, only results on the left side are useful for this)
9. do this until no further entries where found
10. reboot the computer when finished
Please send a reply, if you solved the problem !!!