To answer your questions, first.

Keep your Windows updates, and AV current.
Run CCleaner weekly.
Run Super, and Malwarebytes occasionally, especially, when you feel like your computer misbehaves.
You should be good to go.

Now...


Your computer is clean

1. Download, and install CCleaner: http://www.ccleaner.com/download/builds. Get "Slim" version.
Read CCleaner instruction here: http://www.jahewi.nl/ccleaner/ccleaner.html.
Run CCleaner.

2. Turn off System Restore:

- Windows XP:
1. Click Start.
2. Right-click the My Computer icon, and then click Properties.
3. Click the System Restore tab.
4. Check "Turn off System Restore".
5. Click Apply.
6. When turning off System Restore, the existing restore points will be deleted. Click Yes to do this.
7. Click OK.
- Windows Vista:
1. Click Start.
2. Right-click the Computer icon, and then click Properties.
3. Click on System Protection under the Tasks column on the left side
4. Click on Continue on the "User Account Control" window that pops up
5. Under the System Protection tab, find Available Disks
6. Uncheck the box for any drive you wish to disable system restore on (in most cases, drive "C:")
7. When turning off System Restore, the existing restore points will be deleted. Click "Turn System Restore Off" on the popup window to do this.
8. Click OK

3. Restart computer.

4. Turn System Restore on.

5. Make sure, Windows Updates are current.

6. If any Trojan was listed among your infection(s), make sure, you change all of your important passwords (bank account(s), secured web sites, etc.) immediately!

7. Download, and install McAfee SiteAdvisor: http://www.siteadvisor.com/download/ff.html. It'll warn you (in most cases) about dangerous web sites.

8. Read How did I get infected?, With steps so it does not happen again!: http://www.bleepingcomputer.com/forums/topic2520.html

9. Let me know, how your computer is doing.

NOTE If you're currently using Norton (Symantec), or McAfee security tools (antivirus/firewall), I strongly recommend switching to some other product, as soon, as your subscription expires.
- To uninstall Norton, always use Norton Removal Tool: http://service1.symantec.com/Support...05033108162039
- To uninstall McAfee, always use McAfee Consumer Product Removal Tool: http://majorgeeks.com/McAfee_Consume...ool_d5420.html

Free alternatives:
1. Firewall - Windows firewall is fine, however it offers only one way protection (inbound). Your personal data is not protected from being sent out. For an excellent two ways firewall, and an antivirus in one package, check:
- COMODO Internet Security: http://www.comodo.com/
2. Antivirus (use only ONE):
- Avast! free antivirus: http://filehippo.com/download_avast_antivirus/
- Avira free antivirus: http://www.free-av.com/en/download/index.html