To Enable ClearType on the Welcome Screen, open the Registry Editor (Start, Run, regedit) and look for the following keys:
HKEY_USERS\.Default\Control Panel\Desktop\FontSmoothing (String Value)
HKEY_USERS\.Default\Control Panel\Desktop\FontSmoothingType (Hexadecimal DWORD Value)
Make sure both of these values are set to 2 and you'll have ClearType enabled on the Welcome Screen and on each new user by default.
HKEY_USERS\.Default\Control Panel\Desktop\FontSmoothing (String Value)
HKEY_USERS\.Default\Control Panel\Desktop\FontSmoothingType (Hexadecimal DWORD Value)
Make sure both of these values are set to 2 and you'll have ClearType enabled on the Welcome Screen and on each new user by default.