First make a shortcut to skype if you dont already have one
if you have a shortcut to skype right click it and hit properties

if your on a 64 bit operateing system the target should say

"C:\Program Files (x86)\Skype\Phone\Skype.exe"

put at the end of it /secondary

onece youve done that it should look like

"C:\Program Files (x86)\Skype\Phone\Skype.exe" /secondary

if your on a 32 bit operateing system the target box will say

"C:\Program Files\Skype\Phone\Skype.exe"
just add
/secondary to the end of it
that is how you use 2 skype accounts at onece on windows 7
now you can use 2 skype accounts at onece on the same computer