Sounds like a classic ‘HOSTS file hijack’. An easy way to verify such an attack is to run ‘HiJackThis’ and look for O1 entries such as the following:
O1 - Hosts: 216.177.73.139 auto.search.msn.com
O1 - Hosts: 216.177.73.139 search.netscape.com
O1 - Hosts: 216.177.73.139 ieautosearch
If a repeating IP number pattern is found, any of the listed website names are all likely being undesirably hijacked since multiple entries are all being redirected to the same IP address.
You can always have HijackThis fix these, unless you knowingly put those lines in your Hosts file. (Know what you are doing here or ask for assistance in these forums before proceeding.) Many anti-spyware tools allow you to 'lock down' your HOSTS files to help avoid such occurrences.
While formatting and a clean install may solve the ‘immediate’ problem, the pattern of behavior shown by this user will likely ensure a succession of continuing problems (and your involvement) unless they are shown and are prepared to observe basic survival steps.
They need to start with or upgrade to a current and up-to-date anti-virus tool as one of their most basic security steps. In addition, insist that the virus checker really needs to have (and remains enabled) auto update capabilities and is renewed yearly. Unfortunately, dialup is not generally conducive to sustainable consistently executed security steps.
The next most important basic step is a firewall prior to beginning any ongoing interaction with the Internet.
See the following link as a good starting point and to help convince a user of easily addressed perils:
Basic PC Protection Steps – Starting Off Right to Help Keep It Right
Users always need to observe the following Simple Precautions:
A computer has no business being on the Internet (nor any reasonable expectations for continuing health prospects), if it doesn’t have all of the following – reliable and up-to-date virus checking, a firewall(s), up-to-date ‘critical updates’, and antispyware tools.
Vince