If you have antivirus software, now is the time to update it and run a
full system scan. Since malicious software can be very hard to detect
you typically need to scan your system for malicious software with
/several/ of the better online scanners (Kaspersky, Eset, Trend Micro,
Panda, Sophos, Symantec etc.) If necessary, submit a HiJack This log to
one of the expert web sites that analyze these logs.