@ Xanza: Not true. Ubuntu/Linux are operating systems just like Windows/Mac OsX. As such they can and do become infected! https://help.ubuntu.com/community/Antivirus
Your computer will not be slower if you dual boot, as pointed out, only one operating system is running at any one time.
Why not try and eliminate the infection first...
The key words here are SAFE MODE with Networking!!!
Download, (if you can't get on-line, have a friend download and copy to disc/flash for transfer) install, update and then in SAFE MODE* run full scans with these programs...
** http://www.malwarebytes.org
http://www.superantispyware.com
http://dl.surfright.nl/HitmanPro36.exe
**Note: Malwarebytes should be run in 'Normal Mode' unless that isn't possible!
*** Important, when downloaded/installed/updated disconnect from the internet ***
Then re-start.
Try running a couple of on-line scans afterwards to be sure...
http://housecall.trendmicro.com/uk/
http://go.eset.com/us/online-scanner
http://www.pandasecurity.com/homeusers/solutions/activescan/
*Note: On start up (before Windows loads) keep tapping either F5 or F8 (be aware that some manufacturers use F8 for system recovery!) then use arrow keys to highlight 'Safe Mode with networking' and hit Enter/Return, click on a user account, enter the Administrator password (if you don't know it, there probably isn't one so leave it blank) and hit Enter/Return.
©Techno