verus?

You are victime of a scam. If you pay, you'll loose 100 pounds with NO garanty of ever receiving anything in return. The scamer will probably, at least try to, use your information to empty your bank account.

Your computer is probably not fully up to date, and the scammer exploited a known vulnerability for whitch a patch was probably published months, or even years, ago.
You probably run Internet explorer of a version of 7 or less. It's probably UNPATCHED.

Open the Internet properties. Check EVERY settings. Correct any setting that have been changed.

Check your firewall (Windows do have basic integrated firewall that is still beter than nothing). It may have been set to prevent all internet access.

Press Ctrl+Shift+Esc to summon the task manager. Check for any abnormal process. Kill it.

Check for any applications or programms that you don't remember having and uninstall them.

Using another computer, get a good antivirus like AVG or Avira (both offering an excellect free version). Download the latest virus definition.
Save those to an USB stick. Install from that stick. Perform a manual virus definition update. You need to do a manual update as the computer can't access the internet, or may have been set to prevent you from accessing the sites from any antivirus provider...
Run the AV and correct any found problem.

Get Spybot and install it the same way as the AV. Do a full scan and correct any problem found.

Reboot your computer after the scans even if not asked.

Check if you can now access the internet.
Turn ON Windows auto update and install ALL proposed patches and correctifs. It can take a LOT of time if you never performed that task before.
Get the latest version of Internet explorer you can install on your computer.

A good idea would be to get and use some other browser. You have Chrome, Forefox and Opera that are popular. There is Safari from Apple, but I don't recomend installing it on ANY computer running Windows or Linux. If you search, you may find some others.

I realy hope that you won't have to reinstall Windows and everything else.

Electro
August 2012