This actually confuses me.
The only thing i can think of is Dust or a problem with the hard disk.
Does the laptop feel hot in any way? Do you hear the fan? If so, open the case up and look for dust on the motherboard and in the system fan.
Do you hear any clicking? Do you hear a humming? If so the hard disk MAY need replacing.
Also, see how much ram is in there, check if the amount is compatible with windows 7. what you need is:
If you want to run Windows 7 on your PC, here's what it takes:
1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor
1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit)
16 GB available hard disk space (32-bit) or 20 GB (64-bit)
DirectX 9 graphics device with WDDM 1.0 or higher driver
These may or may not work, if it doesn't work i recommend you take it to a technician and have them troubleshoot it. But i hope that I have been of help, and most importantly: Best of luck!!!