The boot.ini file is one way along with the other information MS provides like
If you are logged on as an administrator, you can manually configure DEP to switch between the OptIn and OptOut policies by using the Data Execution Prevention tab in System Properties. The following procedure describes how to manually configure DEP on the computer: 1. Click Start, click Run, type sysdm.cpl, and then click OK.
2. On the Advanced tab, under Performance, click Settings.
3. On the Data Execution Prevention tab, use one of the following procedures: • Click Turn on DEP for essential Windows programs and services only to select the OptIn policy.
• Click Turn on DEP for all programs and services except those I select to select the OptOut policy, and then click Add to add the programs that you do not want to use the DEP feature.
4. Click OK two times.
A detailed description of the Data Execution Prevention (DEP) feature in Windows XP Service Pack 2, Windows XP Tablet PC Edition 2005, and Windows Server 2003
The same two options are also seen in Vista but are useless. In XP follow the instructions for modifying the boot.ini file seen there. Vista now sees the bcd editor used for the new type of boot loader seen there. But that worked when tried in Vista.
XP never saw this problem here at all however except for when IE 7 was still in beta form there was a problem when tried where I simply dumped it until the finished version came out. When going to edit the boot.ini first make a backup copy and save that to a folder.
If currently not seen at the root of C go into the tools>folder options in any explorer window to uncheck the hide protected system files option. Once seen simply right click for properties and uncheck the read only box, close it, and then double click on the file to see it opened up by NotePad. When going to save and overwrite the original choose the save as all files not txt option.
You can always reverse this by either unchecking the read only again after rechecking it following the mod to re-edit or simply overwrite by copy+paste of the saved copy. If the mod doesn't work something else be would then need to be tried before sonsidering the repair install of Windows option.