When does this give the error ?
I don't have that key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aswUpdSv either, so I don't believe changing the path to reflect avast5 would make any difference as that file isn't in avast 5.0 it is ashUpd.exe which is used I believe.
I suggest you try a clean reinstall (this download is for the free version of avast, if you don't have that ask):
- Download the latest version of avast free, 5.0.594
http://files.avast.com/iavs5x/setup_av_free.exe and save it to your HDD, somewhere you can find it again (if you didn't save your last download). Use that when you reinstall.
- Download the avast! Uninstall Utility, aswClear5.exe
find it here and save it to your HDD (it has uninstall tools for both 4.8 and 5.0).
- 1. Now uninstall (using add remove programs, if you can't do that start from the next step), reboot.
- 2. run the avast! Uninstall Utility from safe mode, first for 4.8 if previously installed and then for 5.0, once complete reboot into normal mode.
- 3. install the latest version, reboot.
Of course you could have the registry cleaner clear that entry, but I don't know if there might be anything else, so it may be best to go the long route.