From my experience of "tuning up" snail-speed computers for everyone from my next-door neighbour to a local school to my grandmother, I've always found that, as a general rule, you shouldn't have more than 40 processes running when you have no windows open.
To check this, press Control + Alt + Delete (click "Start Task Manager" if you're running Windows Vista or Windows 7). In the bottom-left corner it will say "Processes: X". For example, with all windows closed mine states "Processes: 30".
These running processes are critical to the running of Windows. Many processes host 'services', for example the service which hosts your Internet access or the service which hosts your themes. What a lot of people don't realise, however, is that every time you install a program it usually installs a service with it. This means that every time you start up your PC, services for all the programs you have installed also start. Software such as Skype and iTunes are notorious for installing multiple services which can really bog down an underpowered machine.
By clicking the Start orb, typing "msconfig" and pressing enter, you can alter which services and programs start with your computer. If you're not entirely sure what you're doing, stay away from every tab other than "Startup", or you might do more harm than good. Under the "Startup" tab is a list of every program which starts with your computer. Have a look through them and decide which ones you need and which you don't. Remember that all these programs can be started manually as and when you need them, so you probably don't need them all to start with your machine.
As you can see from my Startup tab, I have disabled software such as "Google Updater" and "QuickTime" from starting with my machine, as I simply don't need them using valuable system resources.
As previously mentioned, you should also check how much of your hard drive you are using. If you have less than 15% free, you are approaching the "danger zone" and should consider a hard drive upgrade or a program and document cull.
If this doesn't help, or if you're not confident in your ability do perform these steps without causing more problems for yourself, see if anyone you know has a deeper knowledge of computers - they should be able to help you out.
Based on the symptoms you describe, I very much doubt Fibre Optic broadband will help you out much. Even bottom-end ADSL speeds (~2Mb) are enough for problem-free web surfing.
As a sidenote, I have a 2Mb ADSL connection and have little to no problems when the whole family uses the Internet at the same time. It isn't lightning-quick but I never find myself waiting more than 5 seconds for a page to start appearing. Don't be drawn in to the marketing they'll throw at you. Once they have you caught on their hook, you'll likely be tied in to a long contract and won't be able to get out if you decide it isn't worth it further down the line.