Sure. Stop using it, <s>.

How much RAM you got? How much stuff you got running in the background while
you're running RegClean? How big is System.dat? Have you tried running
SCANREG /OPT /FIX from a Command Prompt Only startup (that will probably
hang, too, but it's worth a shot.)

See the first article in my sig for helpful suggestions.

The stall is probably due to corrupt HELPDIR entries....I have run acoss it before.

MS MVP Alan Edwards has answered this question many times, so I will let him answer
it again:

<quote>

Try running RegClean with a command-line argument:
REGCLEAN /L

This will create a log file (called RegClean.LOG) in the same
directory as RegClean. It will be a *very* large text file.
When it stalls, open up RegClean.log in a good text editor or Wordpad.
See if you can pick an error. If it is not obvious, then post the last
12 lines and someone may spot the fault.

It will probably stop at a line like this:
HELPDIR = " ???k"

Use Regedit.exe (Start-Run-Regedit)
Search for that string (Edit-Find or Ctrl+F) and when you find it,
highlight the HELPDIR key in the left-hand pane, rightclick and Delete
and confirm the deletion.
Press F3 to search again. There will be two or three such strings.
Delete as you did the first one.
Note: Don't have the "match whole string only" box ticked when doing
the search for the culprit string.

An alternative is to search for HELPDIR in Regedit and keep on
pressing F3 until you find the first one that is obviously wrong. Any
others will be close by.
Mine was no. 74 of 191 occurrences, so this can take a while in
Regedit.

<unquote>

I vote with Gary--only use a RegCleaner as a last resort.  Here is my
standard blurb on your problem:

If RegClean stalls when you run it, there is a bad entry in the registry
which must be removed so RegClean can complete its operation.  Go to the
Start Menu, Run and enter the path to RegClean's folder and enter the
command:  regclean /L  For example, my folder is on E: drive so my entry
looks like this:  E:\tools\system\regclean\regclean /L  Run RegClean using
this method and a log will be created in RegClean's folder.  Once RegClean
has stalled, use WordPad to open the log.  Scroll towards the end of the log
and see if you can spot an entry that looks something like this:  HelpDir =
" ???k"  The information after the = sign is the bad data that causes the
problem.

Open the registry editor (regedit.exe) and do a find on the bad data value
identified above.  If you are not familiar with the safe operation of the
registry editor, go here for information:
http://home.satx.rr.com/badour/html/registry.html  Once the bad data is
found,  right-click the HelpDir entry in the left pane and delete it.  Click
the F3 key to continue the search and delete similar entries that are
identified.  When the search is done, close the editor and try RegClean
again.