It’s a bit of a hack as with this solution, Skype’s memory usage will grow linearly with every additional instance of the Skype client you run (about 40 MB are required per instance), but at least it seems to work fine on Windows XP:
http://www.tradebit.com/channels/software/110543/multiple-skype-accounts-on-one-computer/
Note that the double quotes should be simple double quotes, not typographical ones. So for 2.) the link’s destination should be sth like
%windir%\system32\RUNAS.exe /profile "/user:skype2" /savecred "C:\Program Files\Skype\Phone\Skype.exe"
(Of course you need to adjust the paths and user to your environment and settings)
Alternatively, particularly if you use Windows Vista, you could try this free Skype launcher (I haven’t tested it):
http://forum.skype.com/index.php?showtopic=88055
Since this launcher doesn’t seem to use dedicated Windows user accounts on your box, you’ll have to disable Skype’s auto-login feature in order to use different Skype profiles.