First of all check if Msg Plus! truly is gone: check if C:\Program Files\MessengerPlus! 3 folder is still there..if so then it's not gone and you can restart it by starting msgplus.exe through taskmanager (ctrl alt del > file > new task).
Next if you have Windows XP you can set Msg Plus! hooking to alternate mode:
- Plus > preferences > miscellaneous..under Messenger Plus! Automatic Recovery Options, set it to "Alternate".
- Reboot
- Start MSNM and check if it's still in alternate mode
- Ctrl alt del to go to taskmanager and in processeslist end msgplus.exe
- Now restart MSNM and see if Plus! appears in the menu, if so "alternate mode" is working fine.
- After checking you can remove Plus! from startuplist by going to: start > run ..type: msconfig <enter>, go to startuplist and uncheck MsgPlus (this step isn't really needed, if need be Plus! will switch to "Allternate" by itself, just check if it's still set to "Alternate" every now and then).
Alternate mode is only available in Windows 2000/XP. When you set hooking to "alternate" Messenger Plus! will be started when you start MSN Messenger (or Windows Messenger). Make sure you got no programs running preventing writing in the registry whilst setting it to "alternate mode" (an example of this sorta program is AdWatch, part of AdAware SE).
If you use another OS, try "default mode - forced".
If Msg Plus! truly got uninstalled (wich i doubt), redownload it from
http://www.msgplus.net and install again...make sure there's no program preventing writing in the registry when you install.
/ 
