plz help ... huge problem when upgrading SZ7 to windows 7

hi,
I use vaio vgn-sz79mn ... windows vista business
and every time i try to upgrade or do clean install for my windows to windows 7 this happens :

1- everything works perfectly fine.
2- after about a month the laptop starts to become very very slow.
3- after that i get the blue screen of death and i lose everything.

this happened to me like 3 times.

now this is how i upgrade my windows :

1- i insert the CD and let it do it's job.
2- i download the drivers from Sony's website and i install them.

so what am i doing wrong ?
please help me
and sorry if you didn't understand something because English is my second language .

 

It seems likely that if there was a fundamental problem with your notebook / Windows 7 installation then it would occur much sooner than a month. Without further information it's very difficult to say why you are having issues so much later.

Did you ever experience a similar slowdown with Vista? Are you using an SSD instead of the original hard drive?

 

yeah i forgot to say that with windows 7 every time i shut down a message shows saying :"there is a program preventing your computer from shutting down do you want 1- force shut down 2- cancel ( i think ) "
and then in less than a second the laptop shuts down without letting me to choose from the two options.
PJF ... thanks for your help but no i didn't experience a similar slowdown with Vista. and i use the original hard drive + 1TB external hard drive from WD
and of course the M2 adapter that comes with the laptop i leave it always inside the laptop .
the 1 TB WD http://globaltech-ow.com/Products/Storage devices/images/TTB.jpg
the M2 http://ecx.images-amazon.com/images/I/51yBPINli6L._SL500_AA300_.jpg

and thanks

 

any help please ?

 

Usually, when the laptop becomes slow over time, it's because of the bloatware / malware that gets unintentionally installed... Do you run any firewall, and install anti-virus? Do you tend to click on spam emails / visit sites which should not be visited?

 

mmmmmm i use BitDefender Total Security 2010 and of course it turns off the windows defender .
and no i don't tend to click on spam emails or visit sites which should not be visited.