I am using win xp sp3. Will Webroot keep me protected?

Hi edud
 
Welcome to the Community Forums.
 
Yes, it definitively should. Please see below re. the system requirements as posted on the Webroot site: 
 
PC & MacOperating Systems

• Microsoft® Windows® XP 32- and 64-bit SP2, SP3
• Windows Vista® 32-bit (all Editions), Windows Vista SP1, SP2 32- and 64-bit (all Editions)
• Windows 7 32- and 64-bit (all Editions), Windows 7 SP1 32- and 64-bit (all Editions)
• Windows 8 32- and 64-bit
• Windows 8.1 32- and 64-bit
• Mac OS® X v.10.7.3 “Lion”
• Mac OS X v. 10.8 "Mountain Lion"
• Mac OS X v. 10.9 "Mavericks"
• Mac OS X v.10.10 "Yosemite"

And just to make sure that all will work well given that you must have quite an elderly system if you are running XP, please also checking the Minimum Hardware Requirements below:

• Intel® Pentium®/Celeron® family, or AMD® K6/Athlon™/Duron™ family, or other compatible processor
• 128 MB RAM (minimum)
• 10 MB Hard Disk Space
• Microsoft Internet Explorer 7.0 and higher, Mozilla Firefox 3.6 and higher (32-bit only), Google Chrome™ 10.0 or higher
• Internet access

If you pass all of the above then you should be good to go.
 
Please note though that you are using a version of Windows that is inherently vulnerable to attack by dint of it's age and the fact that Microsoft no longer supports/patches it.
 
Please let us know if you have any further questions.
 
Regards, Baldrick