running XP home

My computer currently loads upto a point, then just restarts. This then brings up a menu asking if i want to restart normally or safe mode. Each way brings the same problem, a blue screen flashes (too fast for me to read) then the computer restarts, so i'm assuming a start up file has corrupted.

Now the real problem, my XP cd has disappeared much to my dismay. The one CD i always keep in a safe place seems to have gone and after a thorough search i don't hold up much hope of it returning.

So, first of all.

-Does it sound like a problem that would be fixed by simply doing a fresh reinstall of windows?

-If i got hold of another XP home cd, are they individually serialized or will i be able to use my current serial number (presuming it will prompt me if the XP home is already installed)?

- If i have to buy another CD anyway.. can i upgrade to XP Pro and then just install this overtop (without disrupting anything i have saved on there)?

I realise this might be a little confusing, so if anything needs clearing up i'll be on as often as possible to do so. Main thing is getting my comp back and running as soon as possible!!!