IT Support Event Logging Software??

Hi everyone
I work for an IT support company and we want to introduce monitoring for the following:Event Log critical errors,Anti-virus updates and services,Backups,Disk space,CPU Usage,Memory Usage,Network usage,Hardware Changes and Exchange monitoring.I would like to be able to monitor these remotely and get e-mail alerts while sitting at my desk.I have googled and most softwares are a bit too expensive or really just do too much.Also trying to avoid having to install software on the PC’s i will be monitoring if thats possible.Thanks in advance to all who reply.