Old .net Windows app needs update - and decompile source

I have an old utility app we wrote internally for helping to organize files and folders for people. The app no longer works well on newer windows systems. On xp and vista it was solid but on win 7 and 8 it seems to need some updates. The big issue we have is that we only have the EXE for this app. It was written back in 2007 by a contractor and we didn't catch source at the time. IT is only 150kb in total size, just EXE no other things needed for it to run. I think it was written in VB.net and I would like to decompile and look to move it to c#. I also want to update it to use any newer OS hooks for file system events. I know it checks file system watch for file activities and then has some scheduling processes so it can run at midnight or selected time. Next I want you to run through the source and look for any issues, race conditions or other things that need to be tightened up to make it a production ready app to roll out to the rest of our team. So really we just need some help by a well seasoned c# person that still remembers coding for desktop apps :) I know you cant bid much without at least seeing the app so if you message me I will share the exe with you. I can tell you I tried to decompile using jetbrains DOTpeek , free tool [login to view URL], and it seems to work without a problem [login to view URL]