What qualities do you look for in a Trading Computer?

Thanks for correcting me, I am no pro at operating systems but I have been using all of the above operating systems for more than 30 years,
I definitely don't agree with the claim that xp would be safe, there are numerous ways to highjack a pc running xp, without the the user doing mail, browser or anything on it, just by having it online is a huge security risk, especially without updates, your trading strategy could be at risk, stolen and spread on the internet,
that is the main concern here. ofcourse if you are behind a NAT firewall that would make it a lot harder, but most people only have a software firewalls.
not sure about the bandwidth but I have to believe you on that, I always thought that poor bandwidt gives poor latency. but apparantly not.

My strategy stolen? That is a very special case, I doubt using a newer windows would prevent that and I do not believe that any ones strategy posting or reading here on FF is important enough, but well ...

Hmm, that is maybe a difference to Sweden but here in the UK (or Germany where I lived before) you almost always get a router/modem combination from your provider which does not have any port forwarding configured by default which means that any high jacking not done via mail, browser or similar must have been through a connection initiated by YOUR computer. However, I agree with you that there are better versions than Windows XP albeit for other reasons.

The thing with trading is that your packages (mostly prices) are very small so there is no benefit in transferring many of them in parallel (unlike traditional file transfer) but it is important to receive each package (the quotes for example) as fast as possible.