Which hosting provider do you use? What version of IIS/Windows do they use?
You can try to add a web.config file to your root
<configuration>
<system.web>
<customErrors mode="Off" />
<compilation debug="true" />
</system.web>
<system.webServer>
<rewrite>
<rules>
<rule name="Imported Rule 1" stopProcessing="true">
<match url="^(.*)$" ignoreCase="false" />
<conditions logicalGrouping="MatchAll">
<add input="{R:1}" pattern="\.(gif|jpe?g|png)$" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" negate="true" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" negate="true" />
</conditions>
<action type="Rewrite" url="/index.php/{R:1}" />
</rule>
</rules>
</rewrite>
<security>
<requestFiltering allowDoubleEscaping="true" />
</security>
</system.webServer>