Papa Lazarou
Living in a De Zerbi wonderland
There should be a windows product key on a sticker somewhere on your laptop - download or borrow the installation discs and use that key when prompted.
Seeing a it looks like you need to nuke the entire system I would recommend having a go at installing Linux (mint or Ubuntu probably) and seeing how you get on. If you hate it you can still put windows back on but I think you'll find out will breathe fresh life into your system.
Oh and clean out the fan and any vents, overheating causes no end of cockery.
Mines a desktop - but i guess it still applies.