The monitor color profile tells Photoshop and the other color managed programs how your monitor displays colors. Color profile files are installed by putting them in C:\Windows\System32\spool\drivers\color. Then to assign or confirm a color profile for your monitor, you use the Color Management control panel. Under the Devices tab when 'Use my settings for this device" is checked, the color profile currently in used is the one which name ends with (default). For example 'Dell U2410 color Profile, D650 (default)'.

You can download the color profile for you monitor from here [ Register or Signin to view external links. ] 694&formatcnt=0&libid=0&fileid=413637
[ Register or Signin to view external links. ] 694&formatcnt=0&libid=0&fileid=413637
it downloads a .exe file which is simply a decompressor like .zip files. Run it, and in the folder you will find a file with the name DELL-U2410.icm - his is your monitor color profile from Dell. However most likely Windows has already installed it for you.

Now, given your situation, you may have these eventual problems.
First problem.
Your monitor is a wide gamut monitor 102% of NTSC and Windows defaults at sRGB which is about 70% fo NTSC. NTSC is a color space representing the visible spectrum and is used in monitor specs for measuring the gamut.
Assuming that for some time you didn't use a color profile which more closely represents your monitor, Photoshop was displaying images on your wide gamut monitor using the default sRGB color profile which represent standard gamut sRGB monitors and this is very different from yours. Said in other words you were seeing one thing on your monitor while Photoshop was assuming it is another thing. This becomes a problem when you convert from one color space to another and display or reproduce the image on other devices, and in your case when monitor profile is changed to a very different one. To fix this you have to assign your correct monitor profile to the images that were created with the wrong profile and then convert to a common color space like sRGB, AdobeRGB, etc. Assign and Convert to profiles are in the Edit menu.

Second problem.
The color profile from Dell may not be representing correctly how your monitor displays colors. Dell creates a profile that is not measured to your particular unit but for what they assume is an average representation of the monitor's model. Using it, you depend entirely on luck. I have u2711 and I was very unlucky. If you are curious you can study my case which may be also very educational for you and will be able to see clearly the difference between the colors of my monitor and those the Dell color profile represents. Follow the same instructions above for downloading the color profile for your monitor but download the one for u2711 from here
[ Register or Signin to view external links. ] 058&formatcnt=1&libid=0&fileid=365277
then go to that web site from your link [ Register or Signin to view external links. ] and download my color profile that I'm sharing there. It is 'Dell U2711 Spyder 3 + Color Eyes DP User' once you have the color profiles files on you computer, go to this site [ Register or Signin to view external links. ] , upload my monitor profile and the one from Dell and compare. That web site will give a 3D plot of two color spaces in a 3D viewer that you can navigate to see it from all sides (using the Ctrl, Shift navigates faster). The difference that you see made it impossible to create even simple images for the web using Photoshop. I convert from AdobeRGB to sRGB and when Photshop assumes that my monitor displays colors the way they are described in the Dell's profile, all detail in the shadows is eliminated and my images look like crap. I even got better results from creating a profile using this free software [ Register or Signin to view external links. ] it uses the so call eyeometer relying on your eyes for feedback and although the colors were noticeably off, at least the shadow detail was preserved.