Windows Vista Folder disappeared

I want to remove Yahoo Messenger from my startup folder on Windows Vista Home Premium, but C:\Users\Your_Name\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup // ...seems to have disappeared. Can malware make it invisible?
I'm going to check that next and turn on hidden folders.

 

If folder options are not set or changed to allow for hidden folders to be seen you may have a problem finding certain things. Startup folder is a "special system" folder and would fall into the "system hidden" category.

Are you also missing the start button>all programs>startup folder shortcut?
http://www.checkcomputersetup.com/files/automatically_delete_temporary_files/startup_folder.JPG

If it's not missing, right clicking on the Start button, left clicking Explore should take you to C:\Users\user name\AppData\Roaming\Microsoft\Windows\Start Menu. The Startup folder should be there.

Also the shell: command can be used to open a special folder directly from the Start button>Search menu or from the Run dialog. For example, typing the command shell:startup will open the Startup folder (%userprofile%\startup) of your user profile.

If Yahoo Messenger startup is the focus, I believe this is an option found within Yahoo Messenger its self. Somewhere, with in options, will be a checkbox to enable or disable Yahoo Messenger from starting up when windows is started. (look for "general" options within yahoo options.)

See:
http://blog.shankarganesh.com/2007/10/29/stop-yahoo-messenger-from-starting-up-when-windows-starts/

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I just noticed, while in the virus/malware, you have posted and suspect a virus or malware infection. Yahoo may be involved. The wisest thing to do, at this point, is continue to remove or eliminate viri as a possibility. Anything else you do, may spread infection, complicate the cleanup or prove to be fruitless. Hope for the best and good luck to you.