Mac Forums

ok so ive been useing itunes for about 4years now and nothing like this has happened
so yesterday i told me to download the latest version of itunes and quicktime so i did and while i did i was listening to music on itunes. and all of a sudden the program closes by its self i thought nothing of it and went to go reopen it again. it showed me a message saying : that itunes has been eiather uninstalled,moved,or replaced and so i didnt think any thing of it and rebouoted my computer and it worked fine. but then today it showed me the same message and i rebooted my computer like the day before thinking it would work but it didnt the same message showed up.and i tryed to install it again but a message showed up saying another installation is in progress but i have no idea what it is i have nothing else installing

can anyone hlep me reinstall itunes and when i do will i lose everything i have on there??