Your question is a little vague, so I'll try to answer it as best I can. If you are trying to restore your system to an earlier date, then click Start, Help and Support, then system restore. Choose a date that is displayed in bold print. Choose a date before you started having your problem. If however, you want to bring your computer back to a "factory new" state, then do this:
Dell Inspiron laptops have what is called a Ghost Partition embedded on the hard drive which makes it easy to do this. These instructions were copied and pasted from the owner's manual of my Inspiron 1501.
Use Dell PC Restore by Symantec only as the last method to restore your operating system. PC Restore
restores your hard drive to the operating state it was in when you purchased the computer. Any programs
or files added since you received your computer—including data files—are permanently deleted from the
hard drive. Data files include documents, spreadsheets, e-mail messages, digital photos, music files, and
so on. If possible, back up all data before using PC Restore.
To use PC Restore:
1 Turn on the computer.
During the boot process, a blue bar with www.dell.com appears at the top of the screen.
2 Immediately upon seeing the blue bar, press
.
If you do not press in time, let the computer finish starting, and then restart the
computer again.
NOTICE: If you do not want to proceed with PC Restore, click Reboot in the following step.
3 On the next screen that appears, click Restore.
4 On the next screen, click Confirm.
The restore process takes approximately 6–10 minutes to complete.
5 When prompted, click Finish to reboot the computer.
NOTE: Do not manually shut down the computer. Click Finish and let the computer completely reboot.
6 When prompted, click Yes.
The computer restarts. Because the computer is restored to its original operating state, the screens that
appear, such as the End User License Agreement, are the same ones that appeared the first time the
computer was turned on.
7 Click Next.
The System Restore screen appears and the computer restarts.
8 After the computer restarts, click OK.
9 You will now have to run Windows Update as well as Live Update for your virus protection, as these will be seriously out of date.