You can avoid a lot of problems by installing a Linux distro on a USB flash drive instead, or if you have a media reader on the laptop, use a fast flash media to install it to, like SD Extreme. I have a triple boot system myself of windows, kubuntu, and mint on a hard drive, but I often use my USB flash drives with Linux on them instead when on other computers. Since your problem is windows lag time, you don't want to try and then run Linux under it in a virtual system. This leaves 2 options, either boot direct to Linux from hard drive, or boot to it on some other media, such as CD, DVD, (live read only), or DVDRW disc (allows limited file saves), or USB flash drive.
Linux can read/write to windows FAT32 partitions and fairly safe on reading NTFS partitions, but sometimes risky on writing to NTFS, which is what windows 7 uses.
Your first choice is to boot to a CD or DVD "Live" version, but remember if you want to save anything while using it, make sure to do so to the hard drive or flash drive, because the Live versions boot into a ramdisk and nothing is saved permanent, it is gone soon as the computer is turned off or rebooted. However one can effectively use such a "read only" system and save any work done while booted to it, just so long as it's done to some media such as a flash drive or hard drive, not into the home folders of that "read only" system.
The better compromise between that and a hard drive installation is the USB flash drive, because you don't have to chance messing up your windows install and you can save to the home folders in Linux and not lose the data, files, the work you've done, including bookmarks made, etc.
I use cheap but slow loading (5-10 MB/s) 16GB flash drives to install a Linux distro to. It's only slow on booting, but once it's loaded to RAM it runs fast.
The easiest way I know to create a bootable USB flash drive with a Linux version on it is to use the USB Creator program on most Linux CD or DVD distros, or if that fails to use the Universal USB Installer available from pendrivelinux dot com site. If later, after having used the flash drive for awhile you decide you'd like that permanently on a hard drive install, then it can be transferred over to the hard drive, keeping all changes you've made in it, with some minor adjustments done. No need to go into that specifically right now.
Here's a Kubuntu 12.10 version installed on a 16 GB USB flash drive (Kingston DTSE9 for $12 which easily accepts linux installs).
This is how it looks to Windows. Notice if it was lost, most likely scenario is some windows user would not realize it was bootable Linux drive and thinking it new and empty, just reformat it, keeping my data secure from them.
This is how it looks in Kubuntu's partition manager program (KParted). This is the simplest install onto a flash drive, using a single partition for the boot, system, and data (home folders), with the swap file on a different partition. It is "persistent" which means any changes I make to it will be there the next time, unlike a "Live" CD or DVD. I can save data directly to it. Basically it works just like a hard drive would, but smaller and slower on read/write.
One great advantage is the above flashdrive works so far in every other computer I've tried it on, from older socket "A" 462 pin motherboards, socket 754 mobo, to newer AMD Phenom 4 core processor motherboards, an older Compaq laptop with Intel chips, and a newer HP with Intel inside that came new with windows 7.
I can and have transferred it to hard drive later by using the Live CD to setup the larger partitions desired and just copied the smaller ones into the larger using Kparted, (comes in Kubuntu) although I could have used Linux "dd" command to do the same.
Currently Kingston's CompactFlash - Ultimate 600x is rated the fastest flash media out there, but all such are limited in speed to what the media reader can do too. It costs almost $40 however for the 16GB and at that price I'm not sure it's advantage is that much greater over what you get once the system has loaded to RAM anyway from slower flash media that is 75% less expensive. The Sandisk Extreme Pro has the same rating and same cost, but independent testing sites have it running a bit slower on sustained read/write.
I spend time at various linux forums elsewhere and can't tell you the number of times I've read of some sad poor soul who was all ready to run into a Linux distro with no previous experience, all hot to put it on the hard drive in a dual boot with windows, and then ended up crying later about how they'd killed their windows and lost files, especially family photo files, which they had failed to back up.
Even if you do a USB flash install of Linux, there are some mistakes easily made, I'd urge you to backup everything you want to keep from the windows first. You might even want to access the hard drive and disconnect it, then boot from the CD or DVD live linux distro, and install to the USB flash media, the reboot to the USB flash media and once it's determined you have accomplished what you wanted, then reconnect the hard drive. This way you could choose from a boot choice (usually obtained by pressing some function key during start) on which system you wanted to boot into. If you leave the hard drive connected, when you install to the USB hard drive, it will likely also install a GRUB bootloader into the windows drive allowing either system to be booted. You make the choices on how you'd want it to boot.