Here are some ideas:
- Check your system drive for errors, using a bootable USB stick or CD.
If the drive has errors, you will have to replace it, I recommend buying a SSD. Any decent cheap one will do fine for a Netbook.
- Check memory with a bootable MemTest86+ USB Stick or CD.
Do at least 2 passes.
If you have errors, you will have to replace the memory.
- If 1&2 don't work, backup your important data from your drive, as you will have to reinstall Windows. You will need an XP CD with a product key, or XP on USB via Easy2Boot.
Delete all partitions in setup, create a partition and format it with NTFS (quick).
After entering the product key and finishing setup, you will have to install drivers.
Unless you are slipstreaming SATA drivers onto the XP CD/USB Stick, you will have to set the SATA operation mode in the BIOS to something like IDE/Native/Legacy/Compatible, as XP and older do not natively support AHCI without slipstreaming drivers.