My PC is dual booting with Win2k and Red Hat Linux9. I want to switch from windows to linux without rebooting the machine. Are there any software to do this?

This is not possible.

but try VMWARE , or bochs

They let u run a OS from another OS, like u can run windows from inside linux and viceversa

Bochs is going to be useless for really doing this. VMware is expensive.
Your choices are money or convenience.
With the right setup, files can be accessed easily. Programs usually run only in their native OS.
Why is this an issue? Your answer (other than not wanting to reboot) can help point you in the right direction.

the best way is to buy another computer.

Depending on which version of Windows you use, Loadlin may do what you want. Loadlin is a kernel loader for loading Linux from DOS. This HOWTO describes how to use it with Win9x/ME. IIRC, Loadlin will not work with Win NT/200x/XP.

[Edit] Oops, I just noticed you said you were using Win2k. So Loadlin probably won't work for you. But it is an option for anyone using an older version of Windoze. [/Edit]

The simplest way to do this is to get a second box for one of the Operating systems, and thowing in a KVM

Switching Os's is as simple as turning a switch

I'm using Cygwin for some time now, with the XFree86 package you have a powerfull X server for windows. You can connect to a linux box or work localy with unix/linux commands without leaving windows.

Here's a reason:

bios is passworded to HD boot only and you'd like to boot linux without blanking everything.

Would be nice to boot knoppix straight from an exe wouldn't it?

Problem is, everything needs to be cleared from memory and this would require a lot of Windows knowledge, which most programmers of this caliber are less likely to have.

Until then, it's loadlin from DOS

I use VMWare on my computer. On most days I run Red Hat 9 Linux by itself, but whenever I want to I can run Windows 2000 at the same time. With the help of VMWare I can boot up Windows 2000 in a window under Linux. I can also jump back and forth between Windows and Linux.

There are two different versions of VMWare. The Windows version uses Windows as the main host operating system and can run Linux or other operating systems under it. There is also a Linux version of VMWare which is what I use. The Linux version uses Linux as the main host operating system and can run Linux or other operating systems under it.

I have used the Linux version of VMWare at home. In a course I once took at a community college, they used the Windows version of VMWare. The college used Windows XP as the main host operating system and would also run Red Hat 7.3 at the same time under it. Both versions of VMWare work well.

I used my student ID card to purchase the student version of the Linux version of VMWare for about $110. The regular version costs about $300.

There are several minor limitations of the Linux version of VMWare. For instance, when running Windows 2000, joysticks are not supported. In the Linux version, I have also run into a problem setting it up so that both Linux and Windows can use the same USB printer. I think I know how to solve that but have been to busy to try to make the printer work under windows. I have only used VMWare for a few months.

In the college class I took, we would run both Windows and Linux at the same time and we each set up a virtual computer network between the two. Using VMWare they were able to simulate giving each student two computers without really needing to. It was a computer networking class.

see also:

vware-lite

I use "Win4Lin" and it works great for my use:
Delphi,
Crystal Reports,
Access,
Photoshop,
MSN Messenger,
and more.

http://www.netraverse.com/

To clarify pwessions comment..
Win4lin is a program you install on your linux box. It allows you to run windows 98 within linux. It's simular to vmware but it doesn't support win2k or xp.
The only problem running vmware or win4lin on a linux box is if you ever update your kernel then these products have to be reconfigured/reinstalled/patched in order to keep running. If you run windows and have vmware installed on that, you don't run into that problem.

Actually the Win4Lin reconfigure is pretty simple, their installer does most of the work for you and to get the core Windows files installed takes about 10 minutes.

The real nice thing about Win4Lin is that your "Windows" install sits in your home directory in a folder called "win". When I first installed my copy of Windows I just did a zip backup of that folder, then once all my apps were installed another zip backup. Now at any point I can just unzip to whatever Windows install I want.

As long as your not wanting to play games or any video editing, Win4Lin is perfect and their support is very good as well.

Go with the NeTraverse Win4Lin, only if you're looking to do the basic Winders tasks.
i.e. No gaming here. Anything that's going to chew up your CPU, (you may have latest in video cards, but that won't matter), is just going to slow you down. No 'heavy graphic' program will run cleanly. If you're looking to play games, stick with dual-boot.
You can run other, non-intense programs though. I'm running M$Office98, though times for heavy redraws can be daunting, they're not as bad playing games.
In a nutshell, do what you feel is right. I myself, dual-boot. Win4Lin nor vmWare aren't going to be a great help for gaming, but they can be Godsend for the business programs you own.

I like win4lin too, unfortunately I'm a kernel upgrade freak