1. It maybe a hard drive problem. It maybe going bad,
or gone bad. When some drives go bad they take forever to read because
they're constantly trying to recover from a errors. RAM it, if it's still
under warranty .
2. I was facing the same problem,but i restored as. press F8 at boot for startup repair,If it solved, otherwise off the system and boot via DVD Rom by selecting DVDrom as first boot sequence, simply by pressing F12 at the time of boot and choose DVDrom to boot.Keep your original CD of vista provided by Dell with the inspiron in the DVDrom before it will boot via CDROM.follow the on going steps and select repair my computer. Your problem will be solved.
3. Do a system restore first of possible, these are the steps;
1.Open start menu
2. Start ... all programs..Accessories..system tools..system restore.
or directly by command:
In the start search box ( small rectangular box just above start ) type .. RSTRUI and then press ENTER. Now click CONTINUE ..for UAC prompt..
4. Leave it overnight with Startup Repair even though it didn't seem to be doing anything (The hard drive light wasn't flickering). This morning it was still going & it wouldn't let me cancel it, so I used the power button and shut it down. When I restarted it and chose to Launch Windows Normally like you I got the progress bar for quite a while, but it then went into chkdsk. Once this had been completed it shut down and restarted , before doing chkdsk again, although ckkdsk was quicker this time. It did this one more time before the logon screen finally came up and I was able to log on normally. I'm not really sure about what I may have done to get it working again, but it seems fine now. It gave me a message that the system had been restored to the 25th July.
Yesterday I went into safe mode by continually presssing F8 after switching on and then I chose to do a system restore. At the time this didn't seem to work , but maybe it had worked after all. My advice would be to do this first and then do the Startup Repair as I did.
Hey hope this helps. Just got these off the net for you. Here's the link as well..
http://www.vistax64.com/vista-general/229753-dell-inspiron-1525-vista-not-starting-windows.html