iMac super slow bootup

My iMac used to bootup OK, but now I get blank gray screen for several minutes until Apple logo appears, then I get that for a while, then blue screen for a long time before user login appears. Once bootup is complete the computer runs fine.

I tried disk utility - and was able to do a repair, but problem persists.

Should I reinstall the OS?

One time shutting down my wife thought the computer was off but it wasn't and in the morning we discovered it was stuck trying to shut down - might we have 'toasted' something?

Thanks!

How old is your iMac? Year, model? It sounds very much like the hard drive may be failing. In any event before doing anything else, make a complete backup of all your data before the drive completely fails. Use Time Machine or another backup program.

Info on Mac below. What do advise to do next?

Model Name: iMac
Model Identifier: iMac4,1
Processor Name: Intel Core Duo
Processor Speed: 2 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 2 MB
Memory: 2 GB
Bus Speed: 667 MHz
Boot ROM Version: IM41.0055.B08
SMC Version (system): 1.1f5
Serial Number (system): W8606BQUU2P
Hardware UUID: 00000000-0000-1000-8000-0016CB835ECE

You weren't clear about doing a disk drive repair - did you boot from the install DVD first?

Do a drive repair using one of the three recommended methods here:
Resolve startup issues and perform disk maintenance with Disk Utility and fsck

Info on Mac below. What do advise to do next?

Click to expand...

As I stated in my first reply, make a backup first (if possible). Then you can follow through on what member "gsahli" recommended.