How do I know what facilities e.g. Broadband Speed; Javascript;
blockers etc are 'on' my computer?

There are many ways to scan your computer for trojans, viruses, and
spyware.  If you are not an organisation then I would suggest a setup
like this:
1) Sygate free Personel Firewall
2) AVG free antivirus
3) Spybots Search & destroy
4) As an extra source of security you could also run Adaware spyware
remover, I've heard good reports about both Spybot and adaware, cant
hurt to have them both installed, although personally I just use
Spybot.

After all installed - update them all, then run the scans
systematically.  You should be pretty much amazed at what they will
find, especially the spyware removers!

Lastly but by no means least, use Firefox instead of Internet
Explorer, if you want pop up free surfing and less spyware being
installed.

BB

Again if I have missinterpreted your question and you are simply
asking what software you have on your computer then you could use

Everest Home Edition

This will display all hardware and software on the system, its based
on the old AIDA32 software (if anyone is interested)

BB