Some time you need to restore a PC to its factory setting, expecially if it is a low cost PC like the Asus EeePC and, after some years, it is starting to become too slow!
Sure you could reinstall the Starter Windows 7 if you have the appropriate iso file (en_windows_7_starter_with_sp1_x86_dvd_u_678562.iso) extracting it on a USB pen, using for example the Windows USB/DVD Download Tool from codeplex … and you can then insert your product key you can find on the label in the back of the PC.
However there is an easier way to restore that PC to its factory settings, that is reinstalling the OS and have the PC in the same conditions you get when you bought it: at the start up you have to press the F9 key (quickly and several time, till it is taken and the page requesting the restore of the PC is shows). I read that sometime, if you don’t succeed to get that key accepted, it could help to disable the BootBoost going into the BIOS (F2): however I succeeded to let F9 key work at my first attempt, so I suppose you will succeed too if you press that key frequently and continuously as soon the PC start 😉
You will be asked if you want a restore of the PC, loosing all you data (you need to backup on an external storage if you still need them). You have to insert the credentials for the administrator user and then all the procedure run as a wizard so you cannot be missed!
After several reboots, the PC will be like new and I suggest to launch the Windows Update in order you suddenly get at least all the critical security updates (there will be more than 175 updates, more that 638MB to be downloaded!!!).
Then, as usual, I suggest you to create a stand user and always use that user to log in the PC and use the administrator account ONLY when you need to do something that have impact on your PC configuration (like installing a new program or changing some settings): in this way any virus/spyware will find much more difficult to do something wrong on you PC: because you are not using the PC as an administrator, if virus try to install something on your PC, a prompt for the administration credentials will appear and so you can stop that execution if it is not what you want 😉
Moreover I suggest you to activate Defender that is the built in Microsoft antivirus, and disinstall the Asus predefined one that is not much secure and it slows down your PC much more.
Finally, after all the updates are done and you have checked that everything works properly, I suggest you to launch, as an administrator user, the Free up disk space tool (Control Panel -> Administrative Tools -> Free up disk space) clicking on the Clean up system file button, in order to free all the files backup for so many updates (ex. Service Pack backup file).
Every now and then, remember to run also the Defragmentation tool (Control Panel -> Administrative Tools -> Defragment and optimize your drive).
That’s all folks!!